It could be a new model for freelance assignments. A site called Helium is trying to do a similar thing for writers, bloggers and others.
This from Pixish:
On Pixish, you can post an Assignment that asks for exactly the kind of imagery you need. The Pixish creative community can then submit their work, and review each other's submissions. Then all you have to do is pick the winners and send the rewards.
This may sound like some sites you know already - Threadless uses similar "wisdom of crowds" techniques to create t-shirts (and they rock!). But Pixish is not limited to just one product. On Pixish, anyone can create an open call for submissions to any visual project: t-shirts, magazines, websites, books, anything! I made an assignment for a tattoo (but don't tell my grandma).