Flash drives, those small, solid-state, keychain-sized gizmos you plug into a USB port and use to shuttle files around, are all the rage these days. Because they're compact, have no moving parts, and can store, in some cases, as much data as three CDs, you may think they're a good backup medium. And for quick, one-off backups of files you're actively working on, they're not bad. At some hypothetical future date when you can buy, say, a 60 GB flash drive for little more than a hard drive, they may be useful for full backups too. For now, though, they are too small to store a complete, bootable Mac OS X system, and compared to any other medium available, the cost per gigabyte for archive backups is absurdly high.