Alternatively, the client could keep PEX and just wait for confirmation from other peers that the IPs are valid. Flooding then becomes linearly more difficult w

Alternatively, the client could keep PEX and just wait for confirmation from other peers that the IPs are valid. Flooding then becomes linearly more difficult with the size of the swarm. If BitTorrent goes for something like the majority vote in Bitcoin, the effort would be exponential in the size of the swarm, making it relatively infeasible. Further, the swarm could start maintaining a blacklist and throw out the flooders. Bitcoin is a good start in this direction, hopefully the algorithms will trickle down to more common technologies like BitTorrent.