I think you're talking about these social plugins that some sites use. This is personalised for you by facebook. Nobody else can see what you see in your browser when you're on one of those sites. Facebook's partner sites which use the social plugins for their pages don't get any information from facebook about you, your friends etc. (the connection is between you and Facebook, not the site inbetween). I don't use facebook so I'm not aware of all the privacy settings but as a general rule you might want to check to see what you allow to be visible by others. It often stuns me how these social platforms assume that people want to share so many things by default instead of using the opt-in approach.
Of course there is still the issue of whether you even want to trust Facebook "stalking you" across thousands of partner sites that use the plug in because it does mean that Facebook themselves would log visits to those partner sites by you, but only to those sites which use those faceboook social plug-ins and for their own stats (there is no longer any user "off button" for the social plugins that are used by a lot of sites thesedays, such as the facebook 'like' buttons and comment boxes etc, unless you logout of Facebook).http://www.networkworld.com/community/b ... 0-websites
Also note that, in any case, every website logs your IP and which site/page/link you came from to get to their site.