I have mixed feelings over this name changing feature that is proposed.
What I think:
Pros:
1) If you really committed the mistake of incorrectly typing your name at the beginning, you may change it.
2) One can get tired of the same name and change it at their whim.
3) The naming history idea is very good, it should avoid much confusion.
4) If taken, the decision to have very strict requirements as to this feature will be well appreciated, since many people do get a kick out of impersonating another person on sites such as AG. Furthermore, only a dedicated person to AG should have such a privilege; it will reduce many problems.
Cons:
1) One can suddenly regret changing the username and if by a chance, it is taken, the name is lost.
2) If there are no restrictions put on how many times or how frequently the name can be changed, the confusion will be tremendous
3) I am unsure of what will happen to all previous posts and comments made by the person who changed the name, whether they will change or if they will remain with the same name in the moment of the post.
Some of my suggestions:
1) Add notifications to friends of the person under "witness protection program" (just had to) to allow the friends to know that the change has taken effect.
2) Some requirements I recommend would be to have been an AG member for a long time, maybe a year, being a good citizen (meaning hardly any comments erased or other negative incursions), a certain amount of reputation and other point based ranking systems AG decides to implement.