if you buy a used game, play it, sell it back to buy another used game, you're essentially doing nothing to support the developers/publishers.
The title was originally purchased once by the retailer, so they were at least originally paid for the game. These may or may not all be completely sold.
There's a nuance right here.
Before you had purchased it used some number of people had to resell the titles. The number of people who had sold it will directly impact the resale price. So, effectively, there's several conditions on the resale price:
1) demand for the game
2) number of copies available (returned)
3) scarcity, aka number of titles originally sold
4) availability, especially after the sales cycle
A good game people aren't willing to part with will have a resale value relatively close to the original purchase price. Case and point: any Nintendo first-party title. Crummy games will always have a low price unless it's a collector's item. Relatively scarce, high-demand titles will only grow in price over time to the point where they well exceed original sales price.
Then we come to the case of a game that sold extraordinarily well. They've made a killing on it already, but obviously if you sell a few million copies of something there's going to be a few available to pick up. The good game at a better price.
Picking up used games within days of the release? The resale price on any title worth purchasing in the first place is going to be nearly the same as the original purchase price, if you can even find it. The number of copies available in the resale market will only be a fraction of those originally sold, and only a fraction of repurchasers will part with their title after playing it. The longer the sales cycle the more of a tradeoff you'll see, and of course piracy is an entirely different matter.
Mind you, there's other factors to concider with resale, such as reliability. Is it worth 10% off if the disk isn't in tip-top shape? Personally, I'm loath to trust repurchased disks and try to keep it to carts.
It almost seems this push is to enforce something like a perpetual release. Steam and the various platform-based download schemes cater to this kind of thing already. Didn't play Metal Gear Solid on PSX, PC, or any of its rereleases? Well, it's still available.
So, you have the perpetual download plan combined with enforced disk checks. Bypassing DRM is one less thing for publishers to bother with, but it prevents somebody from reselling a product. The product's sales cycle then spans indefinately, with no self-competition.
Or so they think. First thing that comes to mind is falsifying whatever response the theoretical PS3000's responding with or bypassing it entirely with a BIOS hack, etc.
Then you have Nintendo, where Wii hacking is software-side only and its community has made a point of self-regulating to prevent rampant piracy. Not that it doesn't happen, but the most well known tools don't provide for it and many others have the inherant (and usually overinflated) risk of bricking. As far as I know they don't have plans for disk protection, and with the exception of the iQue and the NES haven't implemented anything to prevent it.