There is no requirement that you use your actual name and picture to use this site (see me as an example).
If you want to impersonate the President of the United States, I really don't care. I was a little bit confused about the user in question, but it was more because I couldn't remember who he was prior to the name and avatar change.
Plus he wasn't very good at the impersonation. Come on, Hamilton, Ontario? We all know Barack is from Kenya.
It was a joke from a question a few days ago; the change was never meant to be permanent. However personally I don't feel like you need to know one's name to begin with, several such people in this question alone don't provide it. I can promise that no one actually believed I was the POTUS, nor did I try to impersonate him further than my gravatar/display name.
I never meant to cause a problem, and I still answered questions properly and with maturity. Anyone could just as easily impersonate someone else and no one would ever know (or complain). As the name I chose was obviously not me or anyone else here I thought it was harmless. I think the reaction is a bit overboard myself, but I indented to change my name back anyways, and have done so.
So, what do we do if somebody wants to impersonate a famous person?
Bear in mind that some of this may be legitimate. People will have the same name as a famous person. I used to know a guy named James Bond (he was born and named before the movies came out). What would we do with a George Bush or John McCain, considering that none of those first and last names are actually rare?
I think any regulation would be more trouble than it's worth.
While it most likely won't do much actual harm to anyone, I personally find it somewhat distracting and don't really like it. So I wouldn't mind if such a thing were to be listed as something that's not allowed on the SO family sites.