I think there is a way to improve your chance of winning big - don't invest in startups that serve niche markets. Look at this list of YC companies from last summer: http://www.quora.com/Who-are-the-Summer-2011-Y-Combinator-co...

Don't you think you can you pick out some that had zero chance of becoming massive-scale homeruns, because they served sort of a niche market? There are none that were obviously (to me, or apparently to pg and co) going to be unprofitable, but if you want the next Facebook, you're not going to get it by investing in, say, Codecademy, which, as laudable as its goals are, only appeals to newbie coders, who are a tiny slice of the population.