Publishers should also realize that unless they plan to distribute hard copies of games themselves it would not be wise to potentially damage a business relationship of one their largest distributors of retail games on the market.
The public backlash would be huge if the sales of pre-owned and traded games were put to a halt. Might as well take it a step further and put pawn shops out of business or flea markets as well for selling used products, or online auction or marketplaces, or craiglist.
The Publisher already gets by far a large percentage of profit for the sales of new games, especially when you factor things such as development costs and manufacturing.
The only reason the publishers are complaining is because they don't get a cut of the profits from the price of a used titles sale.
What of the reverse scenario in which Gamestop pays it's customers money when a game is traded in. Are publishers going to take money out of their own pocket to buy back an old product no one already wants. Of course they won't.
Because of companies like Netflix and other online rental places is one of the primary reasons why Brick and Mortar video Rental Chains are going out of business, especially the quite known chain Blockbuster.
The bottom line is all about the money and these companies want to control the retail and distribution themselves and just to maximize their own cut, but they don't take into consideration of the public backlash of it's own consumers that use places like Gamestop for a majority of their game purchases.
Consider the buying and selling of used titles equivalent to recycling, rather then just throwing these products away when the original purchased "license" or "warranty" has expired and is not longer valid. At least someone can get some use out of it rather then no one at all after the original owner decides he/she no longer wants it anymore.