I can't agree more. I had 'the idea' for Airbnb years ago, after couch surfing happily many times.

I'm sure thousands of people had 'the idea' and knew 'not X'. It was really clear to those who had tried the unpaid version there was vast untapped potential in the market for a paid Couch Surfing.

What counted was setting up a system that made the matching process simple, safe, and had critical mass.