“I’m almost afraid not to take the chance,” – This is when it becomes a bubble.

It's that moment when risk aversion flips and the thought of not making money starts to feel like losing it. I'm not talking about opportunity costs in any kind of rational sense. Instead, I'm referring to having the visceral emotional reaction associated with a deep, costly loss because you didn't buy into the skyrocketing market the day before. People become afraid not to invest in what should obviously be highly risky ventures.

Truly crazy bubbles are driven by this paradoxical combination of greed and fear. They both desire instant wealth and dread the sense of regret that would go with missing it. Individually, either of these emotions can drive otherwise sensible people into irrational behavior. Together, they can spur investment in some laughably bad ideas.

This Washington Post piece by Chico Harlan on a group of Bitcoin investors perfectly illustrates the point.

“Us little guys working our butts off, we can’t get ahead,” Cedric Knight, 35, told Melin. “This is a once-in-a-lifetime opportunity to change my life.”

Knight and others visiting Melin were pinning their hopes on a new form of currency whose potential value the world was only beginning to recognize. Millions of people around the world are chasing after fortune by investing in bitcoin — which has soared by more than 2,500 percent in value in the past two years — and other digital instruments known as cryptocurrencies.

...

“What crypto allows is for the masses to be venture capitalists,” Melin said.

“And guys like me, I’m not in the loop,” Knight said. “This is my chance.”

…

Knight, meantime, went home, cooked dinner and then decided to reopen one of the eight cryptocurrency apps he had downloaded. His account had fallen nearly $500 on the day — his initial $1,500 was below $900 — and he said he was “freaking out.” But then, he thought about what it meant to be a cryptocurrency investor. There would be days such as this. But there might be better days, too — much better days. If there were, he did not want to miss out.

“I’m almost afraid not to take the chance,” he said, and soon, he added $260 to his cryptocurrency account.

Some historical perspective from the archives.

"A company for carrying on an undertaking of great advantage, but nobody to know what it is."

Another except from Charles Mackay's  Extraordinary Popular Delusions and the Madness of Crowds. I believe "a company for carrying on an undertaking of great advantage, but nobody to know what it is" was an initial business plan for Groupon.

Some of these schemes were plausible enough, and, had they been undertaken at a time when the public mind was unexcited, might have been pursued with advantage to all concerned. But they were established merely with the view of raising the shares in the market. The projectors took the first opportunity of a rise to sell out, and next morning the scheme was at an end. Maitland, in his History of London, gravely informs us, that one of the projects which received great encouragement, was for the establishment of a company "to make deal-boards out of saw-dust." This is, no doubt, intended as a joke; but there is abundance of evidence to show that dozens of schemes hardly a whir more reasonable, lived their little day, ruining hundreds ere they fell. One of them was for a wheel for perpetual motion—capital, one million; another was "for encouraging the breed of horses in England, and improving of glebe and church lands, and repairing and rebuilding parsonage and vicarage houses." Why the clergy, who were so mainly interested in the latter clause, should have taken so much interest in the first, is only to be explained on the supposition that the scheme was projected by a knot of the foxhunting parsons, once so common in England. The shares of this company were rapidly subscribed for. But the most absurd and preposterous of all, and which showed, more completely than any other, the utter madness of the people, was one, started by an unknown adventurer, entitled "company for carrying on an undertaking of great advantage, but nobody to know what it is." Were not the fact stated by scores of credible witnesses, it would be impossible to believe that any person could have been duped by such a project. The man of genius who essayed this bold and successful inroad upon public credulity, merely stated in his prospectus that the required capital was half a million, in five thousand shares of 100 pounds each, deposit 2 pounds per share. Each subscriber, paying his deposit, would be entitled to 100 pounds per annum per share. How this immense profit was to be obtained, he did not condescend to inform them at that time, but promised, that in a month full particulars should be duly announced, and a call made for the remaining 98 pounds of the subscription. Next morning, at nine o'clock, this great man opened an office in Cornhill. Crowds of people beset his door, and when he shut up at three o'clock, he found that no less than one thousand shares had been subscribed for, and the deposits paid. He was thus, in five hours, the winner of 2,000 pounds. He was philosopher enough to be contented with his venture, and set off the same evening for the Continent. He was never heard of again