John Battelle quotes from this article:
Today our US Search Engine Performance Report: Q2 2008 was released. Analysis of data from our client index showed that Google took more than its fair share of the overall increase in search spending: for every new dollar spent on search in Q2 2008 versus Q2 2007, $1.10 went to Google. Yahoo lost $0.09, and Microsoft lost $0.01. In other words, advertisers are putting all of their new search dollars into Google, and pulling money out of Yahoo Search and Microsoft Live Search.
If I were at Google, I'd be more than a bit worried. Why? Because once you've vanquished your competition, then what?