It's more that the risks are different for the massive revenue-generating companies. In a situation were everybody agrees it's a bubble, Facebook, Zynga, Group

It's more that the risks are different for the massive revenue-generating companies. In a situation were everybody agrees it's a bubble, Facebook, Zynga, Groupon etc. will be under huge pressure to generate more revenues to justify their valuations. If they fall short, their value could plunge; conversely, they might also overreact and make tradeoffs favoring short-term revenue that come back to bite them. So yes, they're in a waaaaaay better position than Webvan and CarsDirect were in ten years ago; but the risks are still significant.