Marketplace as a Service? If that's what this is, and it sounds like it, that would be fantastic. For the last year or two we've thought that a marketplace would be a great potential fit for our app, but simply don't have the resources to build and maintain the infrastructure ourselves.
The Second Life Marketplace (for the virtual world Second Life) is something like this Photoshop Extension, enabling any SL user to sell their creations to other SL users.