Well as far as i know even if your friend has itunes installed he cannot do that. That is what i learnt from my friend. Please correct me if am wrong. As far as i know the ipod syncs with only one computer at a time. So if you want some of your friends songs and think you can just install itunes and get them ... then forget it, coz the moment u attach the ipod to his computer and sync it will remove all your songs already in the ipod. So you either have your collection or your friend's collection.
I seriously cant understand how apple can get away with that??
I really hate apple and steve jobs. The products are good but it is the company i hate. They are way too restrictive and the frustratiing part is fanboys still make them be like that.