Tyler and Cameron Winklevoss

Cameron and Tyler Winklevoss have been many things in a short time: Olympic rowers. Nemeses of Mark Zuckerberg. Characters on "The Simpsons." Now they can add a new label: bitcoin moguls.

The 31-year-old identical twins have amassed since last summer what appears to be one of the single largest portfolios of the online currency that has caused such a stir in financial and technology circles.