First of all, I find it pretty damn hard to believe four and a half million people pirated The Witcher 2. I'd be moderately surprised if four and a half million people were interested in the game to begin with. That has nothing to do with the discussion, but good lord, talk about being overly optimistic about the potential success about your game.
Secondly, buying games second-hand is no better for the game developer than piracy. It's as much "my property" when I pirate a game as when I buy it used, and indeed, the pirate might be doing them more good than buying it at, say, Gamestop, where you'd encourage them to keep preventing the developer from making money off of it. The only real difference is that game developers haven't found a way to work with the pirates; do you think the Gamestop exclusive pre-order BS is because they like them? No, it's done with the mentality of "well, if they're going to buy it there anyway, we may as well try to make them give the money to us".
Put another way, don't whine about pirates, then defend buying games used.
Lastly, not everyone who's pirated a game hasn't also bought it. It's often to circumvent developers' precious DRM, perhaps with a smug grin or a middle finger in the upright position. I've pirated games I've bought myself to circumvent anti-piracy measures, because nine times out of ten they're flipping annoying to deal with. I'm not fool enough to claim even the majority of the people who pirate games do this, but you never see that factored into companies like Ubisoft's tirades against piracy, because they refuse to admit they may be doing something even paying customers don't want to put up with.
Of course, over nine pages, someone's probably said each of these and far better points than I've raised, but hey, I've already typed the thing up.