According to information and proofs unveiled recently, Facebook cookies track you even after you logout, to make sure that they maintain a complete list of websites that you may visit even after logging out to build a comprehensive and sophisticated data about user behavior.
To experiment this yourself, create few fake Facebook accounts. After using them for some time, you will find that Facebook will suggest you your real account as a friend. This is a proof that Facebook knows that all accounts are coming from the same browser, even after you are logged out.
So apparently if you don’t want to be tracked then logging out of Facebook isn’t enough, you will need to clear all the browser cookies (relating to Facebook), or maintain a separate browser (other than your primary browser) to use Facebook, or don’t use Facebook at all.
Making it worse, it appears, Facebook isn’t bothered about this flaw. The guy who revealed the bug claims to have reported this to Facebook through their support and press emails, but of no avail. He says that the has all the emails that he has sent to Facebook over past one year regarding the said issue.
Just to mention, this user behavior or user tracking data is of extreme value for marketers and government agencies. They can pay anything for this data to be made available to them.
After going through the track record of Facebook, one might think that Onion’s this report of Facebook’s link with CIA was probably more than just a prank.