What other businesses can Amazon undermine?

Amazon (AMZN) is getting into the used video game business. It makes sense. Video games should be easy to market through e-commerce. The recession should make used products more attractive.

The news hit video game retailer Game Stop (GME) hard, as it should have. According toThe Wall Street Journal, "GameStop has been enjoying strong growth even as other retailers have been battered by the recession." Amazon may take away some of that growth. But that is the old news.