[Lizard]

OmniFocus will sync with your server automatically when you make changes locally. If your OmniFocus database gets wiped out again, just put those same settings into OmniFocus again and tap the sync button at the bottom of the screen, and it will either pull down the server data automatically, or ask you whether you want to use the server or local data (and choose server).

If you're only using MobileMe for OmniFocus, you might want to look at BingoDisk or other WebDAV providers. Many of them will give you the same functionality for much cheaper. (But check these forums first to see if a particular service is working for other users. Some flavors of WebDAV aren't so cooperative.)