Do you worry about your Steam account getting hacked which will then lead to your card getting raped? Well this new Steam/Steamworks feature will ensure that no one else can use your account but you.
Steam Guard will lock your Steam id to one PC system, meaning that nobody can modify any account settings on another system without your own permission. The system takes advantage of upcoming Intel Identity Protection Technology (Intel IPT), an encrypted, hardware-based feature available with the new 2nd Generation Intel CoreT and Intel CoreT vProT processors.
Users will be notified if someone attempts to use their account on another system without authorization. Setting authorization for other systems is said to be pretty easy, for those who use multiple systems.
The steam platform has over 30 million users to date, so security is definitely high up on Valves priority list.