Outside the Silicon Valley world, there are numerous similar examples. J.K. Rowling's first Harry Potter novel was rejected by 12 publishers, for instance.

The stupidest things can turn out to be hits. I read of a guy who decided to market an electric toothbrush in the early '90s, when that market was considered by skeptics to be mature and saturated. He was quite successful, as it turned out.

I guess the nature of entrepreneurship is that it's entirely unpredictable. Therefore, we can safely disregard the naysayers, even though they are accidentally right 9 times out of 10!