I'm a little bit stunned by the number of Slate readers who take the ludicrous stance, "Who cares if he exaggerates? He's funny!"
This response, which doesn't even rise to the level of coherent argument, evinces the intellectual rigor of a 3 year old, combined with a junior high school "funny = popular = good" sensibility.
The world is confusing and uncertain enough even when we do our utmost to get at the truth, the whole truth and nothing but the truth. And even when people (including autobiographers) try to tell the truth, they are often deluded or blinded by self-interest. But jeez, once you start allowing willful exaggeration, there's no "there" there anymore.
As to the "who cares?" question, the answer is every real person who is the butt of such "exaggerated non-fiction", particularly if the embellishments are not flattering.