Okay, so here's the thing! I recently bought a new iPhone 5C for my girlfriend, and helped her get it running. I made a backup of her iPhone 4S to iTunes and used this backup to set up her new iPhone 5C Everything went perfect - until today, when she had a couple of updates pending in the appstore. When she tried to update, it asked her for the password - but to MY account. Now, the thing is, she had three updates pending. She could manually update two of them, but the third one was the problem. This also happened to be the only one of the three apps, that I also have on MY phone. So - what happened, I guess, is iTunes installed it with MY ownership instead of hers. Now, the problem was solved by simply deleting the app and download it again. But this is surely not a viable solution. Imagine, if we have 30 apps in common. Then she will have to delete those other 29 apps and reinstall them, when they get updated in the future. So, my question is as follows: How can I use one single iTunes to sync, update and whatnot two different apple ID's?