Facebook engineering director Arturo Bejar has shared what personal information the company retains with its tracking cookies. It does not matter if you are logged in to Facebook or not, they collect information for any site that you visit that contains a "Share" or "Like" button. So, if you have ever created a Facebook account it's best to delete this cookie if you don't want them to know what you are doing on the web. Facebook collects: URL of site visited, IP Address, etc. for all those sites that you visits :-S