Playing devil's advocate I'd say P/E ratio is a flawed metric to use when talking about what some of these new startups are worth. A lot of the newer IPO's represent companies that have significant assets in new areas that we haven't necessarily found the most efficient monetization scheme for yet. Pandora, for example, may not have any earnings, but the value of controlling the source of 100 million users music is no doubt quite valuable. Similarly, one might even argue that some of these companies are undervalued. Facebook's mindshare and ubiquitousness among the upcoming generation is without a doubt a new phenomenon, and so one could say that their current valuation approaching 100 Billion is small considering it's only based on the current monetization scheme of advertising (you would also have to argue at the same time that more efficient monetization ideas exist).
tl;dr- It could be unwise to measure new age technology companies with old age metrics when discerning value
Obviously, there are some outliers like Groupon that do create large valuations with little value (arguably)
tl;dr- It could be unwise to measure new age technology companies with old age metrics when discerning value
Obviously, there are some outliers like Groupon that do create large valuations with little value (arguably)