Well, if you factor in the opportunity costs of the capital and talent allocated to unsustainable companies, then there's a good argument that the US economy loses. Every dollar invested in Zynga or Color is a dollar that could have been invested in something productive over the long haul. Every talented programmer that goes to work at a flash-in-the-pan, overhyped startup creates opportunity costs and economic inefficiencies by not working at more productive enterprises, creating real value. The wage and equity inflation created in the job market by overhyped startups leads to similar inflation across the industry, raising operating costs for everyone in the business.

All that hype-based investing does is swap money around between a relatively tiny cohort of people. It doesn't create real value over the long run, and all the real value that is foregone is opportunity cost.