As Lauren Cooney highlights it in her experience, Facebook is victim of its success as it shifted from a personal tool to (re)connect to a mix of personal and professional plateform to network with others (potential clients?). Now people try to figure out how to use the power of the social network to conduct business. In my sense, most of them conduct it in the old way with push marketing without using effectively interesting interactions with potential customers.
Whether you like it or not, you have to accept it. The only thing that makes me angry is the hypocrisy behind a lot of groups. Many group admin use the group to spam people for product, service or events, at least groups like Ernst & Young are honest as they are "sponsored"!
That raises two points in my sens that can be solved.
The managing issue is due to the fact that Facebook does not allow you to edit some basic group features, just with the applications. As a user, you should be able to chose how you want to interact with a group: receive or not messages from the group admin, receive or not notification of new posts, or group modifications etc...
Then, the community issue is due to the lack of real "self regulation" tool. People in a group cannot dismiss an admin of a group or even a person there. The admin has all the rights. In fact that's against the web 2.0 spirit. I am sure that you all noticed the little thumbs up and the cross on facebook's News Feed. They should add that for every member and every post in a group. That would make sens in a web 2.0 spirit and will help self-manage groups. of course the dismissal would be after many people "report" that.
Actually i really don't understand why the programmers of Facebook do not give the user more managing power over their own Facebook's experience. Perhaps that's only made to let more interaction instead of leaving the user to chose to limit them to his will.