I experienced a disaster last month: My desktop PC's hard disk crashed. It gave no warning (at least, none that I recognized), and silly me, I didn't have a properly organized backup strategy in place. Fortunately, I had been traveling and had fully synchronized my PDA (an older NEC MobilePro Handheld PC); I had not only loaded my current appointment calendar and contacts database but also copied recent files. As a result, I was able to keep working on current projects and restore some of the key information back to my desktop PC.
This synchronization-as-backup worked so well that I highly recommend it to anyone who uses a mobile device--whether it's a PDA, notebook PC, or Tablet PC. If you synchronize Outlook on your mobile device with your desktop and keep copies of recent key files in both places, you're giving yourself quite a bit of insurance against disaster. You still have no excuse for neglecting to implement a full-blown backup strategy (I have one now, thanks), but believe me, this bit of insurance helps!