I think we have now seen that a site can take action based on the referrer field, whether automatically or manually, and that the OP need not assume that he or she is being spied upon. A forum might reject an application simply because the wannabe member Googled in, irrespective of what the Google search term may have been. The link may have been provided automatically. The site may have been saying "Your application is rejected because we only accept people who came from a list of approved referrers and Google is not one of them." At this point I (a) see a whole bunch of (this) forum policy "don't go theres" opening up and also do begin to wonder just what kind of forum it was, and why the OP is worried about who might have been tracking him, but I guess we'll never know. Maybe that's just as well...