Verdeloth: It`s obviously possible, as it happened to several people already.
Most frequent theory is, that each game has several copies set to be for free (like for example 38th and 57th copy).
And if anyone tries to buy exactly the chosen copy of the game he/she will get it automatically without payment.
RWarehall: Nah, it's somehow account based. Your account is somehow selected in case you click it at that moment. Each round may very well be a separate chance though. But with recently past freebies, you get it the first click or you don't. Could swear someone had accidentally closed the window in a past event. Clicked buy now again, and the free game was still there for them.
Yes, that`s also possible.
My working theory was, that there is always a fixed number of copies for free. But it could be also a variable - as they don`t know, who exactly will click Buy now, I don`t think they could prepare any fixed algorithm in such case.
