Facebook tracking details

Thanks to @MarkDansie for spotting an explanation of Facebook information tracking:

About logged in Facebook users: 

• Facebook keeps a timestamped list of the web URLs you visit, paired with your name, 
• Lists of friends, Facebook preferences, email address, IP address, screen resolution, operating system, and browser.

About Facebook users who are logged out:

• Facebook still captures everything except your name, list of friends, and Facebook preferences. Instead, it uses a unique alphanumeric identifier to track you.

Now, though Facebook could still match a name to that 'unique alphanumeric identifier' the company says that it doesn't. But they probably retain the capability to make that match if, say, law enforcement asks them to. And, besides, studies have shown that the information about IP address, screen resolution, operating system and browser configurations is almost certainly sufficient to identify Internet users uniquely.

Why do this? Because Facebook is a business engaged in selling stuff: both information about users and advertising to users. The richer and more complete the information they have, the more valuable their business and the higher their share price when they float. You are what's being sold.
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