A lot? Also irrelevant. All it takes is one for the statement "nobody can see the bubble" to be false. Take the housing bubble for instance. Do you think the people who called that one were successful purely by chance, or does the fact that a few investors observed that mortgage lenders were underwriting loans to people with extremely poor credit and approving loan applications the lenders knew to be materially fraudulent at a massive scale indicate that the call was more of an educated wager? Did they know to a certainty it was a bubble? No, of course not. Was it a very reasonable guess? Absolutely.