This should be upvoted for visibility:
On October 1, 2013, an attacker exploited Ross Ulbricht’s Bitcoin wallet and drained 29,655 BTC from Ulbricht’s accounts. Later, the attacker drained an additional 144,336 BTC from the wallet, stealing a total of 173,991 BTC. At time of theft, this represented over 1.5% of the total bitcoins in circulation.
This raises a major security risk. The threat is not from the client protocol per se – but from the magnitude of the illicit redistribution of funds.
The attacker moved the stolen bitcoin to two different addresses: 1F1tAaz5x1HUXrCNLbtMDqcw6o5GNn4xqX and 1i7cZdoE9NcHSdAL5eGjmTJbBVqeQDwgw. The funds have been transferred several times since then. It is critical that this hard fork be performed ASAP to avoid the risk of further transactions before Ulbricht’s bitcoin can be recovered.