I've never signed up to Quora, but the last time I visited, it looked as though I was logged in which I assumed was via my Twitter cookie. (I don't have a Face

I've never signed up to Quora, but the last time I visited, it looked as though I was logged in which I assumed was via my Twitter cookie. (I don't have a Facebook account.) It's not happening now so possibly was part of some A/B test. That coupled with this passive browsing would be a step too far.