from wired.com: Who owns the single largest Bitcoin wallet on the internet? The U.S. government.

In September, the FBI shut down the Silk Road online black
marketplace, and it started seizing bitcoins belonging to the Dread
Pirate Roberts — the operator of the illicit online marketplace, who
they say is an American man named Ross Ulbricht.

The seizure sparked an ongoing public discussion about the future of
Bitcoin, the world’s most popular digital currency, but it had an
unforeseen side-effect: It made the FBI the holder of the world’s biggest Bitcoin wallet.

The FBI now controls more than 144,000 bitcoins that reside at a
bitcoin address that consolidates much of the seized Silk Road bitcoins.
Those 144,000 bitcoins are worth close to $100 million at Tuesday’s
exchange rates. Another address, containing Silk Road funds seized earlier by the FBI, contains nearly 30,000 bitcoins ($20 million).