Viral marketing is hilarious. Ubisoft, for example, is all about it.
If you've ever been to IGN's forums, you're probably aware of the Ubi VIPs (assuming they're still active, haven't read those forums in while). What you didn't see were the dozens of other accounts on the same IP addresses as those VIPs asking questions about Ubi games, bumping Ubi threads, and doing whatever else to keep Ubi games and Ubi threads in constant rotation on the boards. And, of course, they would post elsewhere to look like the average joe that just plays games.
Dozens.