Oh, I just thought of this.
Ok, so the problem is lots of Gnutella users slowing down the "network".
Well, I don't think that's from the TTL at all. I don't know how Gnutella/Gnotella queries the master server, or how the server finds the IP of any clients, but if it uses any sort of broadcasting (like NetBios) or it has to update the LMHOSTS list frequently (with WINS) or even if they found some way to dynamically do DNS and it has to update the HOSTS file a lot, all of those cause a lot more slowdown than packets running free with high TTL.
A server that has to constantly find where every client is, assign it an IP address, assign that IP to a MAC address, and store that for however long is going to be severely impacted by many people trying to connect to it at the same time, especially if the address resolutions are kept for very long or are dynamically reassigned.
When the source code comes out we'll see.