Some people like to download copyrighted stuff. Actually many do. Personally I only download stuff that the DMCA doesn't cover, like japanese movies, anime, and some other stuff, but i'm not everyone.
KaZaA, morpheous, and the e-donkey network clients have a similar flaw. although searches and indexing is peer-to-peer, the actual file transfer is not. What does this mean? It means your stuff being downloaded and uploaded can be tracked back to your IP address, and people can sue you if your infringing their copyright.
So how does one get away with peer-to-peer filesharing anonymously? Its pretty simple really... just make the file transfer act the same way as the search, send all data through all the nodes in the network, rather than establishing a direct connection. Each host only knows about the direction its sending its data to, it doesn't know if its the destination, or just another node to pass on the data. Its anonymous.
Does this exist yet? YES!
Mute: Simple, Anonymous File Sharing.