Interesting pointer from Francois on the marketing potential of Facebook et al
Check out this post from Emergence Marketing:
"Unfortunately, the reality is that many spammers have already invaded Facebook, Myspace and other similar sites. Go check the walls of the most popular interest groups in Facebook to see for yourself - many are littered with posts that are total sales pitches or with information that is totally irrelevant to the group's conversation."
(from : What is the marketing potential of LinkedIn, Facebook and MySpace)