Codecademy

With software eating the world and very few ways to learn to create it, to Sims it was a very huge opportunity, so by 2011, he built Codecademy in YC, having gotten started, they posted it to Hacker News as a Hail Mary before the Demo Day and that got them about 200,000 signups in just 3 days.

They were everywhere, the press loved it, they were on every 30 Under 30 list, won awards, and more. As a founder, all of this felt great to them until they had to raise to stay alive.

All the press clippings didn't add up to enough $$ money to demonstrate that they'd built something people would pay for.