How to give other users access to parts of a user's POD

Hi

I am wondering what is the recommended approach to allowing a user to share parts of their POD with other users. As a concrete example - say we have an app for managing a user’s music library. The User might want to share a set of songs with a group of other users. Each song could be an mp3 file in the POD and we would want to allow a set of users access to these mp3 files.

From my understanding my app would have to change the .acl settings for these files. And for this the app would have to be granted control permission by the user. But I have been told this can be dangerous as it gives the app full control to do what it wants with any part of the user’s pod. So if this is not how I should be doing it then is there another way?

Thanks
Des