From the news section :
MULTI-SIG * With the integration of BitGo multi-sig technology, Bitstamp is now the first and only major bitcoin exchange to incorporate the industry's best security practices available today.
COMPLETELY NEW HARDWARE INFRASTRUCTURE * The Bitstamp systems are running on 100% new hardware deployed from a completely secure backup of our code and data.
AMAZON WEB SERVICES * Bitstamp is now running on Amazons world-class AWS cloud infrastructure, architected to be one of the most secure and reliable cloud computing environments available.
COMMISSION-FREE TRADING * As a note of thanks to our loyal customers, all transactions conducted on Bitstamp through the end of the North American Bitcoin Conference -- January 17th (at 11:59pm UTC) -- will be commission-free.