This topic also made me dwell on the point that there is only 1 general reason people are disfellowshipped: The acted in a way or failed to cease acting in a way that is in opposition to a current belief being taught by the Watchtower Society.
A person could be disfellowshipped for accepting a heart transplant and the very next day the newest Watchtower magazine is released that states it is now alright to accept a transplant. There would be no change in the decision to disfellowship as it was "wrong" at that time. People are not reinstated when doctrine changes to support the disfellowshipped person's point of view.