No, I certainly wouldn't think of my coworkers as mercenaries for hire, as that's a very simplistic worldview that I don't subscribe to. My net concern is: Will me working at FB be a net good, neutral, or bad for society? I'm fine with neutral, I just don't want it to be a net bad.
I've just been given an offer from Facebook and I have a few days to decide to take the job or not. The ethical implications of what I'm doing are intense. On one hand, a near 400k total comp package is very nice, but on the other hand I don't want to make the world worse off. I think if I could make that kind of money working from home for another company it'd be an easier decision. Unfortunately, I have to play the hand I'm dealt.