Imagine that Hacker News beat us to the punch and had a "let's found important startups" thread. Would you be as positive and enthusiastic? HN is geared toward people who know about startup culture. People who have read PG's essays and spent significant fractions of their lives improving their ability to win at startups.

Compare the HN group to the people who will reply to your post. You're selecting against people who already have experience doing startups. (Those people already have the experience and social connections necessary to start another company. There's no reason for them to take a chance on people in this thread.) Also, fluid intelligence is great, but domain experience is much more useful in the case of startups. Finally, it's important to note that LW posters seem to suffer from akrasia. When the rubber hits the road, LW users seem to flee.

Of course, I have little experience in any of these domains. The LW akrasia correlation is simply my impression, not something based in empericism.