Coinbase chief Brian Armstrong stressed in a blog post that there was no evidence of insider trading "at this time," but also promised a zero-tolerance approach. The CEO said "will not hesitate" to immediately fire anyone shown to be trading on non-public info, and insisted that the company had repeatedly warned employees against the practice. Staff are barred from any trading for "several weeks."

It's not certain when Bitcoin Cash transactions will return to the exchange. Whenever they do, the unusual activity is a reminder that digital currency is still a relatively untamed space. Even with futures trading and tighter regulation in place to add some stability, virtual money still tends to be volatile -- it doesn't take much to create havoc.