>> then we wouldn't have any use for centralized trackers anymore.
So we finally invented emule?
Centralized servers that provide selection, moderation, quality control, information, imdb score etc, is exactly why bittorrent protocol won against all the decentralised protocols.
I dont remember of any credit system in emule, people upload and share just out of generosity. I guess it also contributed to bittorrent success - uploaders probably get some share of tracker site ad revenue.