This is such a cool idea. Why not sell software in iTunes?

But if software authors were to offer their programs through an application like iTunes, the benefits would be immediate. Instead of customers blindly downloading, you could show 30-second demos, just like Apple does with music videos, TV shows and films today. Instead of one-line descriptions, the developer could describe their offering with full paragraphs, explaining the benefits, and happy users could add reviews. And leveraging the iTunes infrastructure, one-click payments and rapid downloads would be a piece of cake.

Talk about a great extension to an already fantastic service.