I wonder if it wouldn't be a good idea for several P2P networks to share the purely network-related parts of their protocols and networks. That should give us both strength in numbers and synergy. For instance, some have speculated that Satoshi's initial goal was to provide a currency that could be used to provide a financial incentive for running Tor nodes.
Nothing (except resource limits) stopping you from running multiple protocols over the same pipe...
As for Gnutella, you can fit a power law with cut-off to the degree distribution but I do not recall how statistically significant it is (p-value).