"My guess is that someone has to move forward with a large direct response ad network that can deliver relevant ads in a very very small ad unit that is easily embedded into the widgets."

I think the appropriate ad unit would be a single sentence, fifteen words or so. Will a successful company emerge to do this or will facebook give their widget developers a way to monetize without a middleman?

I was looking for this exact thing for a small app I'm writing... i figured it was already out there. funny.

Somewhat less than an ETrade user.