Say you have a notebook. You're traveling, and somebody hits your screen with a 2x4. (It could happen.) The system still works, kind of, but you need a new unit ASAP before your old one dies. So, you rush to the store, grab a new machine, and now have to deal with transferring all of your data. Doing this over a LAN-if you have one available--is slow and cumbersome at best. Ditto that for using USB Bash drive or (shudder) optical...