How did the FBI seize 26000 BTC? I thought that all wallets are supposed to be safe. Can you give the technical details?
The FBI gained access to the private keys corresponding to the addresses that were used by Silk Road to hold user balances. In this manner the FBI was able to transmit the funds to a FBI controlled wallet and thusly confiscate the assets.
Clarification on how the keys might have been accessed (speculation):
The software running on the Silk Road server must have had spending access to the Silk Road users' internal balances. Therefore, there must have been a mechanism to unlock the wallet (assuming an encrypted wallet was used). Thus, the pass-phrase would have been available to the program, concluding from the outcome, likely in the files on the server. As the server was probably running when it was seized, they might have been able to access the files directly and thus gain access.