Robert_Charlton - 11:00 pm on Aug 21, 2010 (gmt 0)
If google is recording each SERP result with every letter change then this will really distort impressions on Adsense.
I'm sure Google is tracking behavior very closely during these tests.
But, would they count a view as an impression before you click? Seems to me that, at the least, you'd have to pause for a while before it should be counted.
This feature might result in fewer clicks to the serps page... so, depending on what they do count as an impression, it could end up reducing reported impressions rather than increasing them.
I'd consider what the most desirable behavior would be from Google's point of view. What's the user involvement tradeoff?... the user satisfaction tradeoff?... the infrastructure tradeoff?... and the impact on advertising income, both AdSense and AdWords?
The feature most likely would trigger certain kinds of mental disorders, so the healthcare costs might also be a factor. ;)