The new .Mac Sync feature in OS X "Tiger" makes it easy to keep two or more computers in sync with each other. Mail messages, Address Book entries, Safari bookmarks and other important settings are synchronized with .Mac servers, so your home and work computers (for example) can share the same up-to-date information at all times.

During my recent IT support contract, I relied on this feature to keep my office and home in sync. I also made frequent use of the iDisk feature of .Mac to share files between locations.

.Mac Sync in Tiger is better than iSync in at least two ways:
1. It has more options to sync data from Apple-built applications.
2. Sync services can be used by other Mac software developers.

The second point is a big deal. I already use .Mac Sync to synchronize RSS subscriptions in NetNewsWire and FTP favorites in Transmit. It's a powerful tool that's going to become more useful as more developers adopt it.

The catch, of course, is that .Mac Sync requires a .Mac subscription, which costs US$99 per year (US$179 per year for the Family Pack).

I think it's safe to assume that Apple's goals for .Mac include user loyalty (or "lock-in") as well as long-term annual revenue. To make this work, the service should continue to improve and offer value for the annual subscription fee.

How can .Mac be improved? I think backups are the key.

Since it was first launched as iTools, the .Mac service has emphasized e-mail, file storage, and Web hosting as its core services. Tiger has added a focus on data synchronization, but this feature probably appeals more to users who have more than one computer, not to consumers who own just one Mac.

What would drive .Mac popularity through the roof? I believe that a new "it just works" backup tool, powered by .Mac Sync and linked to iDisk, is the killer app that's needed.

Automatic (backups) for the people
Very few people take backups seriously until they experience a hard drive failure. Most people have to lose some data before they will commit to doing regular backups.

Once the decision is made, however, there's still a problem: most people have no idea where to find their data to protect it. Where is Entourage e-mail stored? How about software serial numbers? If you have an external hard drive, you can just back up your entire Home folder, but this is overkill for most people, and it doesn't make your data available to other computers.

In its default configuration, .Mac Sync is designed to protect Mail messages and settings, Address Book entries, iCal calendars, Safari bookmarks, and OS X Keychains. Imagine how great it would be if Apple provided data backup QuickPicks (a la Backup) in the same preference pane.

Imagine how great it would be if your Mac automatically backed up your essential data as part of its regular synchronization.

The pieces of the puzzle are already there, but they're not working together. Yes, you can use QuickPicks in Backup to discover and protect important data. Yes, you can schedule automatic backups to iDisk using Backup.

I'm suggesting that the Backup QuickPicks and iDisk integration should be folded into the .Mac Sync system so it's accessible from System Preferences. Backup Sync should be set up automatically, out of the box, so that it's one of the nice surprises of owning a Mac. ("My Mac backs itself up automatically?! What a great idea!")

The most valuable part of the .Mac service is so obvious it's nearly invisible. It's the assurance that some of your most important data is automatically stored on a remote server, and can't be lost even if your computer dies. I think Apple should build on this simple and powerful feature.