That is an excellent idea. This might force Gamestop to lose some of the margins they are getting on used games. BestBuy will not be making much on their games though.
Considering most of the used games at gamestop are often only 5 dollars below msrp, it's not much of a loss at all. And most importantly, they are going to rip people out of gamestop's stores to buy at BestBuy.