He mentions that his investment in Twitter is a lot riskier than Facebook, because they haven't found a way to monetize. I'd say that the biggest risk to Twitte

He mentions that his investment in Twitter is a lot riskier than Facebook, because they haven't found a way to monetize. I'd say that the biggest risk to Twitter's business isn't monetization, but replacement (dying like MySpace). Both risks seem slim right now. Twitter has stated their business model is advertising. If I'm recalling correctly, the sourced estimates are that they're at a $200+ million run rate on sales. If they get to $500 million in the next few years, that's a great base, even if it's not on Facebook's level.