P/E's don't apply to Yahoo or Amazon or Ebay or AOL. Sorry, but they don't. The market trades these things on expectations and most everyone believes in the future of the internet.
I know it p*sses off all the "sophisticated investors" at Barrons and the Wall Street Journal. But it only p*sses them off because of the price increase does not match the finantials... it upsets their orderly view of the market.
You're right if you say that it cannot go on forever BUT the internet has not been won yet and we are buying who we think are future winners.
Try finding one of those professionals to short AMZN.. they run like chickens.