First off, thank you for writing this. It’s inspired great conversation around the office.
Fog Creek sold for $425 million with just a $10 million outside investment, all in under 4 years; a 42x return. I’d hardly call that a failure on its own right. Then, if you look at the overarching perspectives that Joel Spolsky, or even Anil Dash, have about software — the belief you espouse doesn’t fit into their worldview.
I think the meat of what you’re saying about building a successful SaaS product is wholly correct, but you’ve picked a strange target to make your point. Calling Fog Creek a failure is like telling me I failed to become an astronaut. I’d have to try in order to fail. Sure, there is missed opportunity, but this is different than failure.
I also wonder if some of the points you brought up about competition would have worked against Trello had they attempted to verticalize or go premium. By staying free, they stayed out of Asana’s crosshairs and were able to maintain a laser-focused value prop in the market. As a result, they maintained a steadily growing user base and were a harmless acquisition target.