Right now, the day's No. 1 most-viewed YouTube video is David Letterman's 9-minute John McCain call-out from last night's show.
Backstory, in case you hadn't heard: McCain canceled a scheduled Letterman appearance because (to paraphrase Letterman quoting McCain) he had to rush back to Washington to work out the financial crisis.
In the video, Letterman expresses his admiration for McCain ... and then rips into him over and over and over, continuing even as he brings in guest Keith Olbermann and cuts to McCain, who turns out to be not on a plane to D.C., but in a studio with Letterman's CBS colleague Katie Couric.
This video was on more than half of the blogs in my RSS feed today. Did you watch it on TV last night? Or was there a link in your inbox this morning? What's so compelling about it?