I was playing the snapshot when i had to turn the game off and on to get the sound working (problem with my headset, nothing to do with the game). I exited through the main menu. When i logged back in my inventory was set back maybe 10-20 minutes, but the world was exactly as i left it.

Caused me to lose some iron i had mined prior to the inventory setback, which isnt too bad but it could probably cause someone to lose something much bigger.