Do you know one of best ways to motivate other people and get them involved? Here's a clue... It's not always as simple as quoting a passage from a motivational book or threatening to fire someone, or screaming at top of your lungs about how incompetent they are :-)
I'm not downplaying motivational material. Believe me, I read it all day long. I'm 100% sold on it. However, it tends to be one of those things that positively impacts person reading it at time. Not necessarily person you want to motivate or inspire. Particularly if they're not type person who reads or listens to it themselves.
The downside of threatening to fire someone can have several implications. Sure you might get immediate spur in productivity you were looking for, but in long run you could end up losing much more then you gain. For example, it can create a sense of disloyalty and distrust in people.
Then there's question of what happens if person you're threatening to fire beats you to it and quits on spot? You say it wouldn't bother you, but is that really case? Essentially you've created a whole other problem. Now you've got rehire someone, spend time and money training them, etc. I think you see where I am going with this right?
So what's solution you ask? Obviously you don't want folks running around unproductive and you want those around you to operate at peak performance.