A new paper, Olson’s Paradox Revisited: An Empirical Analysis of File-Sharing Behaviour in P2P Communities, finds a positive correlation between the size of a BitTorrent file-sharing community and the amount of content shared, despite a reduced individual propensity to share in larger groups, and deduces from this that file-sharing communities provide a pure (non-rival) public good. Forcing users to upload results in a smaller caatalogue; but private networks provide both more and better content, as do networks aimed at specialised communities.
George Danezis and I produced a theoretical model of this five years ago in The Economics of Censorship Resistance. It’s nice to see that the data, now collected, bear us out