I contend that the degree of uncertainty related to the expectation of future profits in the social media companies means that that industry ought to be treated by investors as if it were in a bubble, even if it turns out that the expectations were spot on. That is to say, investors should buy in lightly, and supported by a diversified portfolio. So perhaps the question of whether the industry is in a bubble is not as vital as the media may suppose; the extent of uncertainty, which was clearly evident for instance in LinkedIn's trading at 540 times its prior year's profit, is itself a factor not to take lightly. So call it bubble or not, the difference between known and expected revenues is itself worthy of consideration, and when that difference is significant, the wise and prudent investor naturally treads lightly, even if it seems that others may make out like bandits.
The full essay is at "On the Irrational Exuberance."
