No I believe that is a different problem. I think grey sites use keys obtained through illegal CC purchases or stolen from devs via hacks and those keys are later deactivated. That's different from "used".
I would think if you post a full key here, you don't care who picks it up in the end. (not that that is a problem).
EDIT: the 'other site' handles these issues pretty well, with a bot/raffle type of thing or a "Quote" technique (since only members can reply with quote) to hide the key.