Robert_Charlton - 6:17 pm on Sep 8, 2010 (gmt 0) [edited by: Robert_Charlton at 6:19 pm (utc) on Sep 8, 2010]
At about 56 minutes into the presentation, a question was asked about how they count impressions.
Answer was essentially that a 3 second pause or click anywhere on the page is an impression, and that these are counted as impressions, not clicks. I got the sense that they understand that the effect on click-through rates is something they're going to be calibrating.
I'm not yet seeing the video archived on YouTube, but I'm sure it will be available soon.
[edited by: Robert_Charlton at 6:19 pm (utc) on Sep 8, 2010]