In which video does he explain how to tell the difference between a brilliant startup founder and a crazy person?

You cross the brilliance threshold when you can get others to buy into your crazy version of reality.

So an entrepreneur stops being crazy the moment a co-founder or investor shows up?

Get me one of those!

An entrepreneur stops being crazy the moment somebody pays money for their product.

Have you never heard of Scientology?

That's exactly why I found the full talks! Haven't watched them all yet, will report back.

Edit: Not sure. He didn't mention it in one of the video clips, but may eb addressed in the full audio.