Yes, there are known cases. Here are a few:
"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 shew that dozens of schemes, hardly a whit more reasonable, lived their little day, ruining hundreds ere they fell. One of them was for a wheel for perpetual motion—capital, one million..."
"But the most absurd and preposterous of all, and which shewed, more completely than any other, the utter madness of the people, was one started by an unknown adventurer, entitled 'A 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 100l. each, deposit 2l. per share. Each subscriber, paying his deposit, would be entitled to 100l. 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 98l. 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 2,000l. 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."
This, of course, is Mackay's account of the South Sea Bubble of 1720. There are countless subsequent examples.
(By the way, in case it isn't obvious: I am convinced that the Diaspora guys are absolutely serious and above-board. That is why it might be amusing to pretend otherwise.
And I'm rooting for them too. That's why I'm engaged in the vital project of talking down expectations. How else are they supposed to make a splash at this point?)