Locally stored files in application directory being randomly deleted on iPad, why?

My application on the iPad allows users to browse remote photos on their photo sharing site a开发者_JAVA技巧nd optionally download whole albums of photos to the application's local directory (Documents) for offline viewing. I'm running into a problem where after a user has downloaded several (large) videos for offline viewing, they come back later and find that the video doesn't exist locally anymore, this is perhaps 1-2GB of data. They didn't remove it (which I allow them to), does Apple delete documents in 3rd party application directories?

Thanks

There is a limit on how much space each app may take up. I haven't ever seen any official information on this, but everyone seems to agree that 2 GB is the limit. If you exceed that, the device will start deleting stuff.

I was stupidly using absolute paths instead of relative paths :p