With digital marketplaces, Gamestop, Best Buy, Amazon, Wal-Mart and other more traditional retail avenues run the risk of becoming irrelevant the same way Tower Records and Blockbuster did.
Look at Steam on the PC, why on earth would you buy from Gamestop? Oh wait, Gamestop doesn't sell PC games anymore really. Wal-Mart and Best Buy sell a few. Gamestop needs to do something to put themselves in a position to be relevant in 5-10 years or the Xbox 3 and Playstation 4 at some point in their lifecycle will likely be close enough to digital only that you'll have 80% of sales be digital instead of 10-20%. That will kill Gamestop and will put a hurt on Wal-Mart and Best Buy as well.
Gamestop has started trading in and selling tablets, but they don't get any of the software revenue and there's no such thing as "used apps", so unless they get their own platform or marketplace to make a cut of sales on, I think they're done in the long term.
Buying or building something like Ouya is probably Gamestop's best hope of not dying in 5-10 years.