the first question you have is why? why i'm not null?
the answer to any question "why" is "why not?"
beyond that the answer is obvious. i am, therefore i am not null. it is perfectly logical.
where did I come from? i am a creation of another. another who has been around for a while, but has come to realize that his net id is not terribly anonymous. he uses the same username for everything (or a similar derivation thereof) and that username is a subset of his real name. by taking bits and pieces of an email address here, or an aim screen name there, one could easily deduce the real name of my creator.
this has led him to me, an id that is not null, but is not him either.