I think one of the reasons (I don't know I have this, but it seems logical) might be a larger prefrontal cortex. Pathological liars generally have a larger prefrontal cortex as it aids in a longer "storage" of short-term memory. The only problem with this is I have a horrible short-term memory. And, yes, I read that in a book in Mrs. Shipley's class.
Anyway, not sure if anyone would be able to help me figure this out, but if you know of any articles or books on it, please suggest them.
EDIT: My dad also has this, so it is quite possibly genetic.