IMPORTANT!
If you are using facebook, your personal web activities might be being reported to other companies.
Facebook realeased a program called "Beaon" which most of users doesn't know that it's installed in their profile.
What is a "Beacon"? It's a tool allowed partner sites to track users' activities outside of Facebook and then report them back (even when Facebook isn't opened), where they would then be broadcast to all of that user's Facebook friends. This included making purchases at various online retailers.
Facebook didn't have any option for us to opt out from this before, but after several weeks of complaining from users, they finally released an option tool for users to do so.
it's under your privacy option (link found in top right corner of Facebook).
go to "External Websites"
and check "Don't allow any websites to send stories to my profile"
this will block Beacon to monitor your daily web activies.
read full stories from Arstechnica.com
http://arstechnica.com/news.ars/post/20071205-facebook-sorry-for-beacon-slip-ups-offers-full-opt-out.html