The security model in Dynamics CRM is indeed complicated, and in many cases, that complexity provides needed features. There are occasions however in which the intertwined intricacies of Dynamics CRM’s security make you take a step back and think “Wow, I would never have guessed that is what was causing the problem.” One of these such cases arose when trying to find out why a user with a specific Security Role could add users to a Team, but could not remove them from the Team.
by Dan Fink