What about using the rating system that Shareaza uses?
It's called ghost rating, and will prompt for rating if the file is aborted and deleted when downloading, or if it's deleted from Raza's library.
If you could add it and compitable with Shareaza's one, it will leak out on eachother and result in safe networks
I saw this in the bounty list, and this would be a nice idea for the one that wants to develop it!
Gratz, Neglacio