How is this so? By default, Facebook users have been opted into a new Facebook Ads program which places your image in select advertisements based on partnerships (read a profitable selling of your likeness) that Facebook has made.
According to Facebook:
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.While most users would be OK with their likeness being used to advertise a product that they are a fan of on Facebook like Snickers or the World Wildlife Fund; fewer would likely be happy to see their profile picture being used to pimp dating services and the like.
Fortunately it's very easy to opt out of this asinine decision by visiting the "News Feed and Wall" section of your Facebook settings. Cheryl Smith, the aforementioned "Hot Single," has more detailed opt out instructions available for those who need them.
For a company that was just criticized for calling dibs on everything posted to Facebook; enabling this feature for advertisers, especially without an announcement to users, flies in the face of its attempts to work with users for an agreeable environment.
If you don't want to end up with a slew of vulgar wall posts or having your boss and coworkers think you model for singles dating websites on the side, you best opt out pronto!
Clarification: There are many innocent uses of your profile picture by Facebook that fall under this opt out form including using your profile picture on Fan Pages and on Fan modules (like the one to the right of this article). The trouble comes when Facebook lets a company advertising "Hot Singles" use your profile picture because you have not taken steps to become a fan of "Hot Singles" like you would for WalletPop or any other company with a fan page on Facebook.