MobileMe syncing appears to have been having some bugs lately. I've never had any problems before but I've recently been hearing of people having all of their data corrupted, or MobileMe stop syncing entirely.
I now have had my calendar data corrupted on MobileMe. The bummer is that I added 4 events with my iPhone that didn't sync to my laptop before dying. I'm now having to restore my calendars. Sucks.