While this doesn't have to do with Table Top RPGs directly, most gamers play more than one medium. As such, I want to direct everyone to Penny-Arcade today, where Gabe is asking people to sound off on how they feel about buying games used, versus buying games new.
This does, however small it may be, have an impact on the RPG industry as well. I know some places that buy back and resell books to people, and you can even get RPGs there. In the book industry this has been standard fair for years.
The arguments are as follows.
Buying New: By doing this you are supporting the developers. The money for a new game, or at least a cut of it, goes to the original developers and tells them that there has been another sale. This adds to the sales number, and is essentially how you speak with your money. Like a product? Want more of it? Buy it, and they'll see that it is profitable. More expensive for you, but good for the industry as a whole.
Buying Used: By doing this you are not supporting the developers. The person selling you a used copy is, if they are the original point of sale as well, double dipping. As far as the developer is concerned, this is much akin to Piracy for computer games. People are playing the game, but they have received no money for it and thus do not know about the sale. This is the cheaper option for the consumer, but long term is bad for the industry since it means there is less visible support for the things you like.
Gabe has asked people to email him (gabe [at] penny-arcade[dot]com) and sound off on their views of it. I'm also inviting you to sound off here if you want, especially on how you see this could potentially affect other areas of gamers. (Though, at least we table top gamers don't have to worry about Game Stop making a huge business model out of double dipping from the devs)