A Bitcoin conference in New York.

Ari Lewis was a high school student in Long Island, New York, when he bought his first bitcoin in 2012. It cost less than $10, he recalls.

This May, as the price of a single bitcoin climbed towards $2,000, Mr Lewis graduated from Ohio's Case Western Reserve University with a business management degree and a new job: co-founder of a small cryptocurrency investment fund called Grasshopper Capital. Eight wealthy people invested a total of $2.2m, lured by the soaring value of bitcoin and other cryptocurrencies.