Ask HN: Web Services to enable users to sell digital goods on your website?

Hey all, I'm curious if any of you know of a web app or service online that enables users to sell digital goods via your website and split the revenue?

For example: say I own a big photo sharing website and I want to allow my users to offer to sell photos from their portfolios like SmugMug or others do. Basically, I want a piece of software that manages that transaction from beginning to end and is easily integrated into my site (the download, collects income, manages the revenue split between content owner and community, etc.).

My niche is different than this, but it certainly seems like a needed service. Perhaps it's a startup idea in and of itself?

Any feedback appreciated - Thanks!

Lucas