It's not just risk. It's complexity. Groupon is a single product. No single product is going to put human colonies on another planet. No single company, or even single government, seems likely to do that. What, precisely, is Sequoia or Kleiner supposed to throw a giant check at? The rocket maker? The rocket fuel maker? The habitat designer? The logistics and supply companies? The cryogenics company? Lots and lots of moving parts and interdependencies involved, and no apparently clear winner to take the lion's share of the financial upside.