It's not really enough to predict the outcome, you need something concrete to actually bet on, and you need to time things right (particularly for the pessimist

It's not really enough to predict the outcome, you need something concrete to actually bet on, and you need to time things right (particularly for the pessimistic bet). For any bet that involves purchasing bits of profits you you could be right and lose money because because the government generally won't allow the entire economy to implode. By the time a bubble pops literally everyone knows they're in a bubble, knowing something is a bubble doesn't make it irrational to jump on the bandwagon.