So, if on Facebook you visit:
Settings => Privacy => News Feed and Wall => Facebook Ads
Facebook occasionally pairs advertisements with relevant social actions from a user's friends to create Facebook Ads. Facebook Ads make advertisements more interesting and more tailored to you and your friends. These respect all privacy rules. You may opt out of appearing in your friends' Facebook Ads below.
where you can select not to be an unpaid star in some random ads designed to con your friends. Probably a good idea.
At first I was confused, because when I clicked on the Facebook Ads tab, I saw nothing. That's because I had Adblock Plus on. Oh the irony.
The free software replacement for Facebook (ala identi.ca replacing Twitter) can't come fast enough.