I had an idea for a startup around this, and got pretty far in spec'ing it out and seeing what could be done. But what I found, when reading about previous attempts, was that the technical and business side weren't the barrier to entry, it was the legal problems that arose. Whenever systems like this have popped up, it's a matter of days before organized crime and others game the system to do things like launder money.

It's unfortunate, but it seems as though the only entities with the legal and administrative teams capable of handling that are the credit card companies. And they're not particularly interested in micro-payments, it seems.