Here are some points of view use the USB drives for backup form Rick Cook - specializes in writing about issues related to storage and storage management.

The Bottom line: USB hard drives are best suited for backing up fairly small amounts of data, such as laptops, desktops and small servers, where archival backup can be handled by the system's built-in DVD or CD drive. For larger amounts of data or more sophisticated requirements, better to use a tape drive or other system.

Here are three reasons to use external USB hard drives for backup.

They’re easy to use. Some programs offer one-click backup to USB drives, installation is also simple.

They're cheap. The drives themselves are inexpensive, with street prices for external 250 GB USB drives touching $100 and 500 GB drives available for less than $300. This is less than most entry-level tape drives and there is no additional media cost.

No clicks or keystrokes needed. Just insert any USB drive into your computer and the software will Backup or Synchronize your files automatically.

Two way Backup and Synchronize across computers. Automatically backup your hard disk to your USB drive, or your USB drive to your hard disk. Automatically synchronize multiple files and directories between 2 or more Computers.

Non-proprietary archive format. We use the Windows file system to save your backup archives. You do not need any program to access or restore your backup sets - so they will be accessible for years to come (even if you switch operating systems!)

Safety Precautions (Unlimited Undo). Did you accidentally restore to an older version of a file? No problem. By default, We make a backup copy of every file it overwrites, so you can go back to any preexisting version.

Easily upgrade your backup USB drive to a larger USB device. You may wish to perform the exact same backup/synchronize, but on a new USB device. (say you upgraded from a 512MB key to a 20GB portable hard drive.) To duplicate your settings on the new device, simply copy over the \BackupUSBProgram folder from the old device to the new device, and everything should work exactly the same as with the old device!