FileVault is Apple's encrypted file system. I use it on my laptop to prevent me from having one of those "data-loss incidents" in the event that my laptop gets lost or stolen.

FileVault is pretty cool. It keeps all your files in a single big "virtual disk" file. Whenever data is written into the virtual disk, the data is encrypted; when the data is read back, it's decrypted. All this encryption and decryption is done transparently. And the disk is automatically mounted when you log into the Mac, with the encryption key being protected with your log-in password. All in all, it's pretty slick.

But FileVault has also caused me to lose data--and on more than one occasion. Usually the data loss happens when my battery dies on a long flight. My MacBook is pretty good about shutting down before the battery dies, but a battery can go out of calibration. When that happens, sometimes the Mac just loses power. When this has happened to me in the past while I was saving a file, I've lost the entire directory where the file was being saved. Now that's annoying.

The other failure mode that I've seen with FileVault, one that's far more troubling, happened to me on Sunday night. My computer got real slow, the disk kept spinning, and eventually I had to power it off. When I turned it back on, I discovered that every file that had been written over the past 10 to 20 minutes was filled with corrupt data.

I keep excellent backups, so this wasn't the horrible problem that it could have been. Yes, it did take me eight hours to reconstruct all the data on my laptop, but I was sleeping for most of that time. It was the laptop that was doing the work, slowly copying the data from one of my backups back to the laptop.

Periodically wiping out your laptop has another advantage, of course: it lets you pinpoint the problems in your backup system.

Frankly, I always treat my laptop as if it is on borrowed time. Between drops, theft, and buggy software, data that's on a laptop is always living on borrowed time. If you aren't constantly backing up your laptop whenever you have an Internet connection, you're making a mistake.

Wall Street Journal tech columnist Walter S. Mossberg is fond of saying that Macintosh users don't need antivirus software. For example, in today's column about "craplet" software on new PCs, he writes,

"An excellent way to avoid or minimize the craplet problem is to simply buy an Apple Macintosh computer. New Macs don't have any craplets displayed on their desktops. On a new Mac, no third-party software is automatically launched when you start the computer, and you don't need antivirus or antispyware programs because the Mac is essentially free from those menaces."

I agree with Mossberg that antivirus software isn't needed for the Mac today. Nevertheless, I run antivirus software on my Apple MacBook laptop. I've also recommended to my father that he run antivirus software on the Mac Mini that he has at his home.

I run antivirus software on a computer that doesn't need it to protect myself against a legal risk, not a technical one, since I use my Mac for Web banking. There is a risk to Web banking, of course. One of those risks is that somebody will get your password and drain your account. These days, many brokerage firms that offer Web banking have some kind of guarantee in which they promise that they will reimburse you for any money lost as a result of unauthorized transactions. But there is a hitch: they will only reimburse you if you are running antivirus on your computer.

For example, Schwab's privacy policy (revised July 1, 2006) states that customers should keep their computer and browser software current with security updates, install and update antivirus and antispyware software, and use a personal firewall. Apple's Mac OS has a built-in firewall, but it doesn't have built-in antivirus or antispyware software. So if you were using Schwab and lost money for some reason, Schwab wouldn't have to honor its guarantee if you were not running antivirus. My brokerage company has a similar policy.

This policy is not just for Web banking. One of the organizations where I work demands that I have antivirus installed on my computer before I put that computer on the company's local area network (LAN). Not having antivirus installed is a security offense.

What's truly ironic here is that the antivirus programs on the Mac spend most of their time looking for PC viruses, not Mac viruses. That's because, as Mossberg points out, there are few, if any, actively rampaging viruses that affect Mac users. It's tempting to think that this is because the Mac is a superior operating system, but it's really just because the Mac is the minority. If Apple ever gets popular--really popular--then we're sure to see spyware and viruses on the Mac, just as we see them on other computer platforms.

Indeed, I have seen spyware-like programs on the Mac before. A few years ago, my wife had her Mac's Web browser loaded up with toolbars and other "helpful" programs that monitored every website she visited and sent this information back to a few large corporations in California that used them for marketing purposes. Such programs are widely available today. Download them onto your Mac, and you, too, can have a Mac that's filled with spyware.

SBook is an advanced personal-information management program that runs on the Macintosh. The program lets you enter information in a free-form way: no bothering to put phone numbers into phone fields, e-mail addresses into e-mail fields, and so on. But unlike other free-format systems, SBook then applies advanced artificial-intelligence technology to recognize what you’ve typed. SBook can distinguish between the names of people and the names of companies, between cell-phone and fax-machine phone numbers, and so on. It even has an expert system for dialing the phone, so that you can use the same address book in different cities that might have different dialing rules.

I invented SBook’s basic algorithms back when I was a graduate student at the MIT Media Lab. The algorithms were pretty simple, but they were also really fast--even on a computer with a 25-megahertz processor and 16 megabytes of RAM. The following year I dropped out of the Media Lab program and took a job at NeXTWORLD magazine. A few months later I took the ideas and bundled them into the first version of SBook. I even set up a company to sell the program, but I didn’t get rich because the NeXT market never really got large enough.

I ported SBook to Mac OS X after Apple Computer purchased NeXT in 1996 and made NeXTSTEP the basis of the company’s Mac OS X operating system. Rather than try to sell SBook, this time I just made the program available for free at the website www.sbook5.com. The time had long since passed when you could sell an address-book program for $150. But since SBook still offered a lot of features that even Apple’s built-in AddressBook didn’t, I maintained the program and slowly added features--like the ability to export addresses to the iPod’s address book, the ability to sync with Apple’s AddressBook, better support for envelope printing, and so on.

Recently, though, I decided to give up on SBook. I still find the program easier to use than other contact managers--it’s really nice to be able to just copy from an e-mail message, paste the text into a new “page,” and be done. But over the years lots of people have been working to improve Apple’s AddressBook, so it’s steadily gotten better and better. AddressBook syncs with my Treo, it interoperates with Apple’s dot-Mac online service, and there are now plug-ins for Google Maps, Google Earth, and so on. Despite the fact that I made a plug-in architecture for SBook and published code samples, nobody ever wrote a plug-in for my program.

Unfortunately, this is more than just a demonstration of the power of network effects and bundled software. SBook put forth a different paradigm about how data could be stored: instead of forcing people to put their information into neat little labeled piles, the SBook philosophy was that the computer should be smart so that the human user can be somewhat sloppy. But all too often, software developers take a different approach: they require perfection (or at least order) from users, the same way that the computer requires perfection from the developers.

One of my favorite examples here is the unwillingness of most websites to accept credit-card numbers as anything but a sequence of 15 or 16 digits--no spaces or dashes allowed. It turns out that those spaces between the numbers on your credit card serve an important purpose: they make it easier for people to read, transcribe, and verify credit-card numbers. But the vast majority of websites I’ve used that require a credit-card number will generate an error if you try to type the spaces or dashes. With a single line of code, the programmers of those websites could silently remove the extraneous characters. Many websites will instead say something like, “Please reenter your credit-card number without spaces or dashes.”

Another disappointing example is what happened on Martha’s Vineyard in the 1990s when Town of Vineyard Haven bought a software package for compliance with the FCC’s E911 regulations. The town needed to build a geographic database with the location of every house on the map. But Vineyard Haven is a hard place to map: on some streets the house numbers were out of order. In other cases streets changed names, or two parts of the same street weren’t connected together. A more expensive software package could have handled these peculiarities. But the software package that the town purchased couldn’t. Instead, the town simply changed street names and renumbered houses so that the new name-and-number plan could be nicely represented in the database. My house’s number was changed from 10 Spring Street to 18 Spring Street.

Ultimately, names, street addresses, and telephone numbers are nothing more than a compromise among human nature, law, and technology: it’s certainly easier for programmers to force people to do a better job structuring their information than it is to write software that can handle a potentially limitless set of special cases. And in the end, it might even be cheaper for society to force people to eliminate their representational differences and adopt clear and well-defined standards. But we do lose character and novelty as part of this great regularization process.

In any event, I’ve given up on SBook, have published the whole source code at www.sbook5.com, and am now exclusively using Apple’s AddressBook as my desktop contact-management software. At least I’m not stuck using Microsoft Outlook.