Dozens of times, I would guess, because dozens of startups we've funded have given up, and usually they consult me first.

Which is the first go: Money or motivation?

Usually money. A startup can change what it's working on, so as long as there's money left, they can simply restart if an idea seems hopeless.

When motivation goes first, it's usually because the founders had a falling out.

What is the typical circumstance where you tell the founders to quit?

When they're out of money and they say they want to.