tim222 - 7:45 pm on Mar 19, 2008 (gmt 0)
Page load times can be affected by the ad itself, as well. Especially now that Google will be serving ads with that set cookies and contain web beacons. Those events are out of the publisher's control, but they're capable of slowing down the display. At least the display of the ad. I'm not sure if it can slow down the whole page.