I was in gamestop the other day because I happened to be in the mall and needed to kill some time. I saw they had the Ico Shadow of the Colossus Collection on the shelf, which I had planned on buying at KMart when it was released the next day (I had $20 of credit there). A salesman asked if I needed any help, and I just asked if the game was already available to buy, seeing if I could somehow manage to get it early. Of course, he gave me the correct release date, but than asked if I wanted to preorder it, putting $5 down or paying for the whole game outright and pick it up tomorrow morning. I kept my snarky comment to myself, but why the hell would I want to do that? Why pay any amount of money on something that I don't get to have? There's never a situation where gamestop will give me a free game and then expect me to pay for it a week later.
I've worked in retail long enough to know that there are absolutely no guarantees. I also know from our good friend The Internet as well as a few other personal anecdotes I've heard directly from people that gamestop will happily sell your "reserved" game out from under you at the drop of a hat. This is probably because real money in the immediate present is worth more than hypothetical money in the future (especially when it's the same amount). This is referred to from my painfully obvious business classes as the "time value of money." So why does gamestop have common money sense, but it assumes (often correctly) that it's customers do not. I have a much higher likelihood of getting a popular game on release day by NOT preordering, so I can go track it down at another retailer, rather than wait for another shipment to my local store (by which time the price will probably have dropped from what I originally paid). And then again, it's not going to break my heart if I can't play a game in its first few days of release. It's not a major problem psychologically and I certainly wouldn't risk my hard earned cash on it.
It's not just gamestop either. Target currently has a promotion where if you buy a 12 pack of Dr. Pepper, you get a free $1 preorder for Battlefield 3. There is no way in hell Target can possibly be honoring every preorder sticker that comes attached to a case of a common soft drink, as well as every other person who wants a copy and didn't preorder. It's utter nonsense. Even preorder bonuses are fairly easily to obtain even if you don't preorder, either by picking it up in the first week or by ebaying a code or two. Besides, I've yet to see any preorder bonus that caused me to think twice about my stance on the matter (except maybe LA Noire, which all preorder bonuses became available a few months later at a reasonable price). Ooo, a secret gun! Extra bullets! Fancy armor! Really, you'd do that for me?