I for one am a fan of rebates, at least being under the assumption that the savings are greater than if they didn't exist. My Dad has recieved literally hundreds of rebates (he's obsessed), and uses a very methodical tracking procedure. He makes scans of everything he sent in and all the rules, etc. Then simply files them by date. If more than a few weeks have gone by since the max estimated arrival time he calls the company. He does think some are scammers, because after calling them the rebate arrives three days later (in other words, they only mailed it because he called). But there are other conclusions that could be made. There has been only one rebate he has been unable to receive. He made about three calls and then said forget it, because it was only for $15.
It is easy to argue that this process is a big hassle, which it is. But it all depends on how much you value that extra $20 bucks or whatever. He estimates that at least 95% come back no problem. He is also very familiar with the process and doesn't really make mistakes filing for them, so that helps too. Yeah, it's incredibly annoying, but some think it is well worth it.
I also have wondered if the companies can make much just sitting on your money making interest. They are just holding it for good 2-3 months.... I don't know, but it could add up.