Many sites today use widgets from facebook such as the Like button, list of friends who are fans of that site and so on. While it may be a nice feature, I perceive it to be a serious privacy intrusion, because facebook most likely stores information about which sites you visit.

I also heard that when you are not logged into facebook, it still tracks the sites you visit (probably with a cookie) and once you log in attaches the data to your real account.

For now, I want to keep using facebook, but I would like to block just these widgets so it can't track me. Is there any Firefox extension which could do that?