Keith Olberwho?

So the blogosphere is lit up with the story of the "feud" between Keith Olbermann and Bill O'Reilly. At the Television Critics Association's summer meeting, Olbermann reportedly opened his session by whipping out a mask of O'Reilly and offering a Nazi salute, a stunt the head of Fox News called, "over the line."

So, I just have one question - who's Keith Olbermann?