Via Tyler Cowen at Marginal Revolution, a study on the effect of "bad apples" on group dynamics, also highlighted on NPR's This American Life. The bad applies include the "depressive pessimist", the "jerk" and the "slacker". The lesson from the research appears to be: groups live down to the level of their worst performer. Except that a very skilled leader can diffuse the effect.
This post, linked to from the above, references McConnell's "Rapid Development", a very good book on the process of software development. I'd like to think I was good in dealing with bad apples, but I wasn't. Disliked conflict too much to be consistently good.