I think it's worth observing when the early birds in these 'obvious spaces' emerge simultaneously. We had an idea that we wanted to develop and were tempted to apply to a fair number of incubators. There was, though, the concern that if we did so, we might end up hurting ourselves through the disclosure and discover competitors in our 'obvious space'. Was a concern we had. Maybe you don't echo it. I'm sure several individuals who believe their ideas are novel will.

Just so there's no uncertainty about this: we have never, in 4 years of doing this, told a startup we funded about an idea we read in an application from a group we didn't fund.

The explanation for this is pretty simple: the groups we like, we fund.

That's incredibly honorable of you guys, and thank you! But the explanation I don't buy. If you dislike a group, and choose not to fund them, their idea still might be pretty good. (IIRC, one or some of your essays mention that the greatness of ideas and the groups behind them are somewhat independent of each other).

In this case, what incentive do you have to keep the idea to yourself, and not tell/hint at it to a funded startup?

Your word and reputation are certainly worth far more than a single shared idea. Those are pretty strong incentives.

I would assume that if a VC got the reputation of taking ideas and pushing them to other groups instead of the originators, it would kill their credibility. And without credibility, no one is going to go to them for funding.

Uh, if the space is obvious, wouldn't that be exactly when you'd expect to see competitors emerging simultaneously?