Hacker News Reader

Lots of 324BTC transactions. 324 is how you dial FBI.

You're right, I haven't noticed that. However, quoting Forbes:

> The FBI official wouldn’t say how the agency had determined that the Bitcoin “wallet”–a collection of Bitcoins at a single address in the Bitcoin network–belonged to Ulbricht, but that it was sure they were his.

As I read the article, the address is owned by DPR and the FBI seized the associated wallet.

Since they can't be sure DPR doesn't have a confederate or dead-man-switch process somewhere with the private key, it's not good enough to seize/know his key: they have to move balances to a new address that only they control.