There is a new option under System Preferences | Energy Saver panel.
> Restart automatically if the computer freezes
This option allows you to let your mac auto restart if something happens that OS X doesn’t seem to be able to handle itself. Perhaps you hear already about the spinning beach ball effect. It is spinning and spinning … and you don’t know that OS X is working hardly in the background or this is a hopeless situation already. So if yuo select this option, OS X can decide itself the best time to restart the computer.