By the way, when doing a search to see if this had been posted here I found one related submission, but that stated that the control key needed to be pressed before seeing the choice of Force Quit in the dock. For me the choice was just there without pressing any extra keys.
[robg adds: I believe this behavior has been in OS X since the beginning, though I'm not positive. Basically, if an application is no longer functioning, and the system knows it's not functioning (not always the case), then the dock's contextual menu will show Force Quit instead of Quit. You'll also see such applications listed in red if you hit Command-Option-Escape.]

