I think it is partly about philosophy. Gnutella isn't only a file-sharing system, but a network, which might be used for far more purposes, than just getting mp3s (and some projects already begin with that).
It always changes, evolves, and at the moment the traffic for network communication went down to an average of 500B/s, that's less than 0,5kB/s for leaves and about 1,5 to 2 kB/s for Ultrapeers, while many different clients interoperate. |