In my experience as a game developer at least, the best entertainers absolutely would play around with ideas and work on projects for their own gratification.

In my experience as a game developer at least, the best entertainers absolutely would play around with ideas and work on projects for their own gratification. And on the other hand, Facebook succeeding or not is by definition it having an effect on its audience - if people like it enough to keep using it, it'll work. So if anything it's probably more like making a movie than a technical hack. I think you're drawing a distinction in motivations (audience/no audience) that doesn't really fit. If we're talking about the best of both industries, I think they both work on each type of project.