I know we used to keep our FPs if we weren't going to use them, which was VERY rarely. I know quite a few people who used to actually pull FPs and purposely not use them to keep them for scrapbooks, photo albums, etc.. So I can imagine quite a few FPs went to waste before, especially with the ability to not be able to change them. At least now, if you can't make your 5pm FP, you can check and see if they have anything available earlier or later. I'm sure there is SOME abuse to the system, just as there is with every Disney system (double dining bookings, etc..) but probably not enough to warrant Disney to do anything about it. But now that you mentioned it, I kind of would like to see what those numbers are. Now you've got me curious!
PS - LOVE your signature! I saw the fireworks at Disneyland for the first time ever last month and they play Walt's speech during the show. I cried like a baby hearing it!