iTouch Users from all over have had trouble with many different applications freezing up and having to be reinstalled. Apple has now (hopefully) addressed this with the new upgrade to the iPhoneOS (2.1), for both iPhone and iPod Touch.
However, prior to this, many people have lost the data associated with their apps because of this. I have had a couple inquiries regarding the syncing of mileage logs to the home computer when the device syncs via iTunes. Problem...Apple doesn't allow it!
It's true! Developers are not able to write applications that sync/save data during the iTunes sync process. This is why you'll see a number of applications that email reports (like MileBug), use file transfer apps, or even build custom web sites that allow the backing up of data.
So while this is not the most desirable setup, it's what Apple has given us to live with. We have looked at building a web application that would allow MileBug users to back up their data, but it just hasn't happened yet. So for now, please periodically email yourself a report of your data. Making backups is a good habit for any software you use. Enjoy!