shorebreak - 1:17 am on Apr 9, 2008 (gmt 0)

I don't have any hard data to back this up, but over the years I've seen some specific types of campaigns spend much more on Yahoo (as a proportion of overall search spend) than is the case for 95% of regular PPC advertisers. For example, franchise lead gen comes to mind, as do miraculous-claim beauty products (for lack of a better word).