I'm not betting on Flippa. They've stepped into big boy territory. How long until Google or Amazon hops in the game? I guarantee that either company would quickly dominate the market. Google would dominate simply because they're gangster. Google Plus integrated with search to force adoption by web-masters and small business. Amazon, on the other hand, can optimize any process far better; thus making it more profitable.
I'm not trying to bash Flippa.. I've just recognized that big businesses like to attack new segments only after it has been proven by another company. Then they pounce like ferocious mountain lions and suck the blood (cash) from the poor, wounded animal (business).