In both online and "real world' communities and organizations I have often seen individuals become key figures not by the quality of their contribution but by quietly running off anyone who might actually do the job better. I have seen cases where there is one honored employee who has stuck with the boss for years while others seem to always quit on him or her. What the boss never realizes is the better people didn't quit. They were driven out by the supposedly dedicated employee.
I have seen this especially bad in some open source software programs where there really is no management. Anyone is free to contribute. All you have to do is put up with extreme abuse from a small group of very incompetent hackers who have elbowed their way into the middle of the project. If you complain about anything they are quick to point out that people aren't exactly lining up to help and they have contributed more than anyone.
From a management perspective these people can be very hard to spot. They often show a totally different side to their superiors, giving the impression of very nice people and dedicated workers. It is also very easy to get many professionals to leave quietly with a few well placed attacks no one else sees. For most professionals it isn't worth the fight and they really don't want to be part of an organization where people behave like that.
Have you observed cases like this yourself?
What do you watch for to prevent such things happening in your online community or organization?
How would you handle a situation like this if you are the one being shoved out?
How would you deal with this as a manager who has just discovered it is happening?
How would you deal with this in an unmanaged situation such as an opensource project?