Humility
Fred Wilson tells the story in this extraordinary post of how his investment company, Union Square Ventures, missed the opportunity to invest in Airbnb, one of my favourite peer-to-peers. At the time, the founders had ideas but the service was still a marketplace for air mattresses on people's floors. It was, he says, the classic investor's mistake of focusing too much on what the business were doing at the time and "not enough on what they could do, would do, and did do".