I can understand the drop in Yahoo auctions, but the situation is different from Napster. EBay has always had fees, so once Yahoo added them, too, there was no good reason for anybody who still wanted to sell stuff and didn’t mind paying a listing fee not to move to EBay’s much larger marketplace. It’s possible that if Napster keeps enough of a subscriber base after adding fees that they might find themselves in the same position as eBay: only the people who really want something for nothing will go to the less populated free services, and any second-tier service that adds a fee will lose all its customers to the leader.