I searched the network for some classic adult films but the search results I got back were porn flicks but had nothing to do with the title I typed in. I got back dozens of results, mostly the same ones with different names. When I downloaded then and previewed them they were all Windows Media Files which popped up a dialog telling me that I should purchase a license to view the content.

So it seems to me that someone has figured out how to spoof the search results and give you back results you don't want. I only want to share free content off course.

So my question is: is this the end of Gnutella and should we all now move over to BitTorrent or something? Is Limewire somehow involved in this scheme?

This sounds like a classic case of not recognising bogus files or spam. See both of these:
1. autogenerated spam results & 2. Movie download issues