Yes I would pull the lever. Who wouldn't. You would get a million bucks. Besides, someone in the world dies every 5 seconds... wait, is that how they do it OMGASHWTFHOLYMACRONI. But yeah, even though lives are priceless I want a million bucks over a life I probably don't know.
I'd pull it, so long as I don't the person. Otherwise, I don't care about their lives. People are murdered every minute or so somewhere in the world, so it won't change much.
That, and my conscience isn't so great with things I don't witness, even if I directly cause them, hehe.
Isn't that the plot of a movie? Anyhow, yes, I would pull it many, many times. The world is overpopulated as it is; now if that person was a loved one of mine I'd probably live to regret it everyday, but I, myself, believe money does buy happiness.
That's the problem just like that movie the box.. It can be anyone, even your dearest family members.. I would only pull it if I didn't know the person.