That's a very good question, actually. I'm sure there are quite a few of us who take "interesting startups happen" as motivation enough, but if this experiment becomes routine there might well be a reduction in the number of hours people volunteer for this.
Which probably isn't the best phrasing, but I'm serious about the question, for people on HN the motivation to participate is that it is fun or interesting or whatever, so I wonder how many rounds of votes you can squeeze out of that.