There are a couple of people that I know who are too dangerous to let near you as a leader: 1. One for one people - everything is an exchange for these folks. "If you do this thing for me, I'll do that thing for you." The reason they aren't safe is that eventually the exchange rate doesn't work anymore and you're constantly in debt.
2. Mountain Bikers - I don't mean anyone who rides a mountain bike but I am referring to those people who want to clip in and pedal down hill as fast as they can as they wonder why everyone else is just being a wuss and not keeping up. You might have been on a leadership team or some serving body with these folks. Leaders have a tendency to let these people in because it feels as though big things will happen fast. However, things rarely get accomplished other than the rest of the team gets belittled or frightened away.
3. Hungarian men - Go to Hungary and you'll see why. Something about guys playing chess in a big bathtub worries me.
4. General Managers- These are people who like to have the most say in big decisions but don't like doing the work to tie their own shoes.
Leadership is the opportunity to build people but you have to watch out for those who want in the circle of influence without earning the right to be there.