Facebook just unveiled their new advertising that will turn your "check-ins" and "likes" into advertising. As always, Ars Technica shows a detailed analysis and discusses why this might not be what you, the user, may have intended.
I deleted my Facebook account right around when Facebook started littering the web with their "like" buttons. If you value your privacy at all, you may want to consider not only deleting your account, but also block Facebook from receiving any traffic from you, either via a firewall outbound setting, or by changing your hosts file to resolve facebook.com to 127.0.0.1.
It seems that whenever I think Facebook can't play more fast and loose with their users' data, they surprise me.