I, unfortunately, work for a certain electronic retailer, whom sells pre-owned games en-mass, here in the US. Obviously can't say who, but I'm sure you can figure it out.
I have a seasaw opinion on the used game market. I think it's great, in some aspects, but think that it's horrible in other aspects. Had it not been for the used market, some of the games that I've picked up, and loved, and now follow the studios associated with said games, I never would have taken a chance on. I don't have much time to play games these days, with school, work, and trying to better my health, so if I'm going to spend $60 on a game, it's got to be something I know I'm going to not just play, but ENJOY playing. I now buy games from these developers new...I.E. The Bayonetta Team and Anarchy Reins, or most things SEGA Publishes (don't care what anyone says, I liked Alpha Protocol for what it was, same with Vanquish.)
These are games, that had I not had an oppurtunity to buy pre-owned, I may have missed out on, and not known to trust the people who make these games. Heck until I heard what the team behind the new Devil May Cry game were responsible for, I was insanely hesitant about it. The current market of games, have so many games coming out, at such a fast pace, that it's really hard to decide what's worth the buy, and what's not.
On the flip side, I think that the Used Market has become extremely toxic for some developers. Smaller studios, that have a hard enough time getting by in todays economy, are almost certainly going to be doomed, because production costs are through the roof. The average salary for someone in the industry is about 40k. Assuming a team has something small, around 10-20 people we'll say (15 to average it out) you're looking at 1.8mil in just employees salaries, before going into shipping and distribution, marketing, licensing costs, voice acting costs, and all of this assuming it's a cycle time of 3 years.
Now a publisher will likely pick up part of that tab, but if the game doesn't bring that publisher profit, odds are their next game is going to face some severe limitations, or worse, be closed. Assuming that the game costs, lets say 2million dollars, the game would have to sell something to the tune of like 30k copies, new, to break even. (My math might be off here, but I'm kind of winging it as I write.)
To kind of show the damage that's resulted (and may have been used as an example for all I know, I haven't had the chance to read through the board completely) but the studio behind Heavy Rain estimates that something to the tune of 1 million players have played their game, through use of the pre-owned market, which they estimate is anywhere from 5-13 mil in lost royalties. That's a lot of money.
It'd be wrong to say that the pre-owned market is the soul reason for a lot of the studio closures we've been seeing, but I think that it's fair to say that it's a large contribution to it all.