While each service--except Carbonite--offers some kind of archive of older versions of each document, only a few make it easy to pick which version you want. Backblaze makes you select a snapshot date from a pop-up menu to access versions, and the same is true of Mozy; CrashPlan, by contrast, has an expand triangle next to files that displays each version by date.

Downstream rates seemed to be constrained more by the time a service took to piece together restored files--sometimes instantly, sometimes with long but reasonable waits--than by bandwidth.

Backblaze, CrashPlan, and Mozy also offer services to send your restored files via DVD or on a hard drive. Blackblaze lets you fill a single DVD for $99 or a 500GB drive for $189 (including shipping). CrashPlan charges $100 plus shipping to fill a drive, as long as you return the hard drive. Mozy charges $30 plus the cost of FedEx Next Day shipping to restore data to DVDs at 50 cents per gigabyte.

To make sure everything is running smoothly, set yourself a remember to periodically test retrieving a moderate set of files--perhaps 100 totaling a few gigabytes--to make sure nothing's wrong at the far end that's gone unnoticed.

And for safety-sake, you should also back up at home using Time Machine or another method. If an online storage site goes belly-up or fails to pay its hefty bandwidth bill, you'll want to be protected.