Battlefield 3 has been doing this since it launched, and it's never been fixed (I still hard lock occassionally). You can always power it off with the power button, but the severity of the freeze determines how long you have to hold down the power button (sometimes it's 10-15 seconds).
Defiance froze me a few times in the opening days, hasn't done it again since. It corrupted some of the data on my hard drive once, but oddly enough it was for a game I hadn't been playing recently.

