Google Chrome has decided that you have to press and hold Command-Q to quit. I've used a macro to stop accidentally quitting Xcode and Mail and Safari in the past (see Really Quit? Macro), but now I need the reverse, one that quits Chrome when I just press Command-Q, so here it is.
I think you can turn it off by de-selecting "Warn Before Quitting" here:
What I find more insidious (and arrogant) are apps like MacUpdate Desktop, which pretend to quit with ⌘Q, but leave themselves running in the background. I have ⌘Q macros for those apps that make sure they're really quit.
I actually use Keyboard Maestro to make ⟨Cmd⟩+⟨Q⟩ force quit a few select applications, but notably both Safari and Chrome, as it saves their application state and revives their tabs upon reopening. I think there are probably options, again, within the app to do this, but pfft.
A) Keyboard Maestro doesn't work without its engine, these apps work primarily when launched as the main app
B) It's pretty clear that Keyboard Maestro's engine is still running and it's pretty easy to quit it. MacUpdate Desktop hides itself completely and there's no way to quit it without going to Activity Monitor or Terminal.