Airbnb didn't realize the insight around facilitating payments around accepting payment when they launched. It was seen as uncool and impure at this time in history to charge money for it. The couch surfing ethos was a very like communal, community based, pay it forward thing. To be commercial was extremely import-taste.
Dalton Caldwell and Michael Seibel talk about where the ideas for Airbnb, Coinbase, and Stripe came from. Then they discuss what you can learn from these founders.
To create Rookies Mistakes we asked YC founders: Is there a simple fact you wish you knew when you started your company or a rookie mistake you wish you could take back?
Apply to Y Combinator: https://www.ycombinator.com/apply/