Way back in 2007, Facebook began its march towards what many consider uber-creepiness. Their "Beacon" program connected third-party sites to Facebook and transmitted users' activities to their Facebook profile. One example were rentals from Blockbuster.com - when Jimmy rented "Sex and the City", his entire friends list would find out.
It wasn't intended to broadcast users' private information -- there was a way to prevent broadcast of such information. However, there was no opt-in. That meant a lot of accidently disclosed private info on users' profiles. Beacon was eventually discontinued.