"There's only really one pure peer-to-peer," he said, "Napster has central directory, as does IM." Meanwhile, Gnutella, unlike Napster, works without a central directory.
"Today, the pain of using [peer-to-peer applications] outweighs the gain," Pescatore said. "It's not very efficient from a network point of view. It requires companies to think through architectural issues, putting technology in place for discovery capabilities. Groove's putting the things in place to do that sort of thing -- reliable delivery, security, naming services [user authentication]."
"Right now, to use peer-to-peer to do that in small, ad hoc groups, you sort of have to be a rocket scientist," Pescatore said, adding that that's why many developers are building on a hybrid model like server-to-server.