At a time when regulations, glitches, price swings, forks, hacks, and fraud can’t seem to keep the cryptocurrency-mania down, there’s a new hurdle for it to overcome: the taxman. Coinbase is one the largest cryptocurrency exchanges in the world and its backing by high profile investors like Union Square Ventures and Andreessen Horowitz has given it a certain amount of respectability. But it’s also a prime target for the Internal Revenue Service.