To industry experts, the news of this hack comes as a surprise. Bitfinex implemented BitGo wallet security a while ago, which should make these heists impossible. Multisignature storage requires more than one private key to send funds, yet somehow the hacker obtained at last two. This leads some people to speculate how the BitGo private key was obtained. However, it is also possible the Bitfinex API token for BitGo was abused in the process.
http://fintechist.com/us65m-worth-bitcoin-stolen-bitfinex-despite-bitgo-security/
