Sure, Facebook can see sites you visit which use Facebook Connect in some form, but can they actually "create a running log of the web pages that each of its 800 million or so members has visited during the previous 90 days" like the article claims?
When your browser requests the like button from FB's servers, the request includes a session cookie, and the referer header indicating which page the like button was loaded from. Super easy to log, though it does generate a boat-load of data.
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Wait, how is this even technically possible?
Sure, Facebook can see sites you visit which use Facebook Connect in some form, but can they actually "create a running log of the web pages that each of its 800 million or so members has visited during the previous 90 days" like the article claims?
They can certainly track visits to those sites displaying a Facebook “Like” button or other FB spoor.
When your browser requests the like button from FB's servers, the request includes a session cookie, and the referer header indicating which page the like button was loaded from. Super easy to log, though it does generate a boat-load of data.