A bubble or not?

In economics, expectation laid upon on irrational optimism leads to the formation of bubbles. Market participants chant "this time is different" when the economy takes off with a promising outlook and all news are interpreted positively despite foreboding signs of a downturn. Outrageously high evaluations of businesses/ideas are justified on grounds of unrealistic estimation of revenues. We all believe that we are smarter than our precedents and can avoid the next crash. However, what perplexes me is that most investors are actually skeptical. When they are presented with new ideas and business models, they tend to be suspicious and are rightly so. There is no expert opinion nor past experiences that can be relied on so people proceed cautiously. However, chances are that even though the new venture might be the next Google, most people would ridicule this new business, denying any possibility of its success until everyone else harps on. Only the few who are capable of independent analysis and are willing to nurture the new venture with the necessary resources would end up with the big prize.