Has this ever worked? I'm not being facetious - I just can't think of any good examples where one "idea person" has dumped ideas on a bunch of smart people and good things have come out of it.

Nathan Myhrvold and Intellectual Ventures? Not sure if that's quite what you're looking for, but it's the first thing that came to mind. It's not exactly "good" in a "for mankind" kind of sense, but apparently it makes boatloads of money.

I'd be curious to hear how things are developed at Apple. For instance, is Jobs an idea guy or more of a gatekeeper ("this sucks, do it better")?

The lightbulb I think.