This results in others sites that I browse being able to connect me to Facebook without my permission. Was initially surprised to see my profile photo at random sites that I visit.
That's how I noticed too, I suddenly saw the name of another HN user listed as 'liking' some article on cnn.com and I figured there has to be some kind of underwater tie that I'm not aware of. CNN lost a user, I'm sure they don't care but I do care. I'm really not looking forward to a web of websites sharing information on their users between them, if I decide to give my information to one website I really don't expect it to show up elsewhere.