Well, this is a developer's forum, right? Though Gnutella is great for file sharing, I'm sure there's lots of developers looking to do more with P2P than Gnutella alone is capable of supporting. JXTA provides these capabilities...it's open source, and I'm one of a number of people trying to draw attention to the possibilities.

And sure, it's a bit of advertising for me, but it's not like I'm in this for the money (trust me, there's no money to be made as an author of technical books). But it's more an attempt to get developers interested in JXTA by providing a resource that they can use to get up to speed quickly...