An online marketplace that exists more in concept than reality raises $12.5m online in a matter of minutes, valuing it at $300m. Within a month, that has jumped to $2.8bn.

Another project has been set up with a vague promise to help computer owners trade their unused storage space is worth $350m.

These crowdfunding efforts sound like tales from the dotcom boom, when investors chased up the valuations of companies with the mere promise of a business idea to ridiculous heights. The speculative enthusiasm for the projects — called Gnosis, Storj and Golem — is certainly the same. But they are actually part of a far more bizarre financial phenomenon. These are ICOs, or initial coin offerings. Instead of minting shares via an initial public offering, these companies are minting cryptocurrencies.