A telltale sign of the risks involved in investing in the latest breed of initial coin offerings: The underlying currencies are so volatile that even the ventures creating the new batch of digital coins often sell as fast as they can.

The values of Bitcoin and Ether, the digital currencies that investors use to buy into ICOs, have declined since the sales of the new tokens were held. The drop has weighed on the value of what the startups raised as a way to fund future products or services.