That's indirect revenue - you might have bought the book because of the forum, but Wrox's finance team didn't know that; as far as they were concerned, it was just another book sale. The site itself had no way of collecting money directly from its users (we couldn't really ask people to pay to use the lists), and as such we were told to concentrate on working on sites that did make money on their own - the Today sites, Wroxbase and Wroxdirect. If only P2P had had as much time and effort put into it as the Today sites did, but we can only imagine what it could have been like - internally, there were so many good ideas floating around that were never implemented...