I could vary likely be wrong, but I'm thinking android apps do have a place they can put data that is just for them. there are seemingly allot of risks involved but id certainly hope that if such were possible the dev making it wouldn't be that dumb. I think we need a expert programmer for android apps to give a answer on this.
Data saved to the internal phone memory is restricted to that particular app and cannot be accessed by other apps (barring exploits, root access, etc.). Data saved to the SD card can be accessed by anyone.
