I'd say a large part of BitTorrent's success was the mix of capitalism and communism.

To maximise your speed you had to share, a mini stock-market on each torrent. Then you were encouraged to continue to share after completion.

From memory all the fancy algorithms for sharing didn't really do much and it was just push it out and pull it in as fast as you can that really worked in practice.

It was also interesting Bram opposed encryption on the protocol.

The global torrent library certainly seems bigger than ever. The biggest issue is upgrading existing media to better resolutions.