BitTorrent Kad is one of the only huge scale totally decentralized systems in use today.
I wonder if it could stand up to a big Sybil attack though? Most of the black hats that could do it don't because they all watch illegal movies and have no motive to attack that network. I would bet you a donut the RIAA and MPAA have talked about it, but actually doing it could expose them to civil and even criminal penalties since it would technically be computer fraud and abuse.
Actually I do think that fake peer injections are used. Sometimes there are some fresh new torrents that can show something like 80k seeds and 100k downloaders. Yet you can't connect almost any peers. It's exctly the attack I used against bitmessage, and was fun to perform with edonkey and emule servers. Worked nicely even before DHT based systems. Basically you could down smaller sites by injecting sites IP and port to peer to peer network, because now all nodes looking for peers would try to connect those sites. Afaik, this has been used to introduce DDoS situations earlier. Especially if client tries to connect hosts multiple times and doesn't immediately flag potential peers which it can't connect. But this is all very basic stuff.
I wonder if it could stand up to a big Sybil attack though? Most of the black hats that could do it don't because they all watch illegal movies and have no motive to attack that network. I would bet you a donut the RIAA and MPAA have talked about it, but actually doing it could expose them to civil and even criminal penalties since it would technically be computer fraud and abuse.