Crypto-coin mania illustrates the crazy and not-so-crazy sides of bubbles. Every market mania reaches a point when pitches to would-be investors enter the realm of the surreal. So it goes for “initial coin offerings”, or ICOs.

A new one by a firm called POW invites Facebook users to claim tokens for nothing; when they later become convertible into other tokens, the first to take advantage of the offer could “become worth $124billion…making them the richest person on Earth”, the blurb says.

Not a bad return for no money invested and no risk borne. However bizarre, bubbles are hard to resist: no one wants to be the only one of their friends left out. They can also be financially ruinous. But gambling on a craze, even a highly dubious one, can be about more than blind greed.

The ICO boom is an outgrowth of the emerging, occasionally inscrutable world of crypto currencies. These are a form of money (bitcoin and ether are examples) used in transactions which are recorded on a distributed public ledger called a blockchain.

An ICO is a scheme to raise funds for an enterprise written into a contract on a blockchain. To buy in, punters use cryptocurrency to pay for tokens. Those tokens become the working currency within the new enterprise. A new social network, for instance, might fund itself through an ICO, then allow users to spend their tokens on goods or services on the network once it is up and running.

In successful projects, demand for tokens should rise and early investors should profit. ICOs resemble both a new form of crowdfunding, and a technological leapfrog over the regulations that hem in more orthodox funding strategies. They are also all the rage. Ether, the currency used on the ethereum blockchain, is up by more than 2,400% against the dollar over the past year and boasts a market capitalisation of nearly $28billion. ICOs have so far raised nearly $2billion in 2017.