There is a potential side-effect of the new facebook “like” button, which has currently not reached public awareness, but it probably should.It starts when you leave the facebook website. I usually don’t log out, my friends don’t log out, and in fact most people don’t log out. We all know this is too much of a hassle.Now, if I visit a website which has integrated the “like” iframe, facebook might just know that I am there. Because I didn’t log out before. And why shouldn’t facebook track the referrer combined with the user id of every requested iframe?
