The Wayfair founders also had made millions on selling their internet services firm to a company called iXL years before - so they had the money to fund the venture.
Good point. There's a bit of a continuum at work here. There's the true "Pull yourself up by the bootstraps" story and some "Friends & Family helped" tales. Even though they made some money, I don't think they invested any more than what would be considered a modest seed—think hundreds of thousands of dollars. Considering how many can't build a big business with tens of millions in funding, they seem worth studying.
