timwilliams - 9:42 am on May 25, 2012 (gmt 0)

I'm not completely convinced of the existence of throttling but it would not be that difficult given google's data. They can categorize the type of search a person is doing (nav vs trans) and make a statistical analysis as to what the percentage chance of each individual search converting is without much effort at all.

Now for the WHY. I know we are talking about the serps but this makes sense for both the serps and the ads. Google needs multiple advertisers for adwords to work in their benefit. If there was only 1 dominate advertiser in a niche that advertiser would not have to bid up their ad. Same goes for the serps, if a serp is dominating the sales then the advertisers go away. It's in google's best interest for everyone to make a little money and no one to dominate. Keep us all hungry but nourished...