I just found out that unless you check a box on Facebook then they could be using your photos in their advertisements. I don't know about you guys, but I don't fancy potentially lending my face to some corporation's ad.
You can read more about it here.
Put simply, if you follow these instructions you can opt out of your photos being used in ads. Head over to Facebook and log in...
Settings -> Privacy -> News Feed and Wall -> Facebook Ads -> Appearance in Facebook Ads and click "no one."