I didn't mean to say that they can't do whatever they want, or that they're incapable of helping the world. But if the investor does not expect his investment back, then that would make it a donation, which - as far as I can tell from the article - this is not.

From their page on funding non-profits: http://ycombinator.com/np.html

"Since some people were confused when we funded Watsi, I'd better clarify that the money we're putting into the nonprofits will be a charitable donation, rather than an investment in the narrow sense. We won't have any financial interest in them."