This would be pretty damn easy really. All they would have to do is switch the http file transfer with a chat connection. That is all the limewire team did.

Then if we just create a seperate client that uses a different connection stream so we would have our own designated network for chatting rather then mixing up our bandwidth with the file transfer people.

Chat connections could be secure and verified based on simple PGP connections.

Search key word's and returns are simply unique userID's attached to a nickname.

That be the first working bones for the first decentralized instant messaging system? It could kill AIM and all the rest, if anyone has the balls to make it.