Startups for effective altruists had been on my mind since seeing Paul Grahm's essays, so I'm glad to see someone writing about it. I don't know for sure that the equation turns out better than salaried work, but an effective altruist would at least get more benefit from taking career risks than most other people.
See http://80000hours.org/blog/12-salary-or-startup-how-do-gooders-can-gain-more-from-risky-careers.
The expected value of risky careers like startups if often much higher than less risky careers. However, this is more than offset by peoples' risk-aversiveness due to diminishing marginal utility. But... if you're an effective altruist, the money you make doesn't have diminishing marginal value. So... it seems that risky careers like startups are a good choice, if you're trying to maximize your positive impact.
What do you guys think?