I agree fully, the pillocks who are pushing this approach aren't taking into account the number of people who purchase a brand new game with credit gained from a trade-in. Sure, not everyone does it, probably not even half, but its still a substantial chunk of the figure. Added to that, as you said, its like free publicity. Someone buys a copy of Oblivion used, cause its dirt cheap, goes WOW THATS AWSUM and buys a brand new Skyrim at full whack the next day. Thats a sale they would never have had were it not for the used games market.
Re: the Oblivion comment ... that's exactly what happened to me.
I found myself with time on my hands last fall, so bought an XBox and a couple of used games ... one of which was Oblivion.
I'd been playing and enjoying it for a few weeks when I noticed TV commercials for "Skyrim".
Then I noticed "Skyrim" on the Oblivion map and it clicked in that it was made by the same developer.
So, as I'd enjoyed Oblivion, I went out and bought Skyrim.
It also occured to me today that if the console makers come up with a "can't play used games" scheme, that will likely be the end of video game rentals as well.