Update: a couple of hours after this was posted, a great TechCrunch article appeared based on an interview with Evan Williams, founder of Twitter and Medium. Perfect demo of the kind of audacity that's needed to make a big idea stick.

An anecdote from the TechCrunch Disrupt finals, which I try to watch every time it happens, shows the difference between a fully emerged entrepreneur and one that has potential.

A very impressive young guy was being grilled by the VCs. He's a second-time game developer, having sold his first company for $105 million, he wants to do it again, this time bigger. And he has a real good way of explaining how it's better. I was buying in, ready to write the check until he flubbed a pretty basic question.

His product only works on tablets.

The VC: "Aren't you concerned that tablets skew older, that most young people use phones, and isn't your business depending on attracting young users?"

The entrepreneur: "Well, eh, uh etc."

He talked for a long time, but he didn't have an answer.

It pissed me off because the answer was obvious.

His game is going to be so incredible that it will sell tablets. Kids, adults, everyone is going to have to get one just to run this software.

Now, to pull this off you have to have a PhD in Chutzpah.

Steve Jobs could have done it, and made you feel like an idiot for asking the question.

Anyone actually could do it, if you really believed it.

That's why it was a very good question to ask this young dude.

You say you're thinking big.

Here you are on the big stage.

Tell us how big you're thinking.

Moral: You have to believe your own story.