Using search habits to gains insights is set to be a major influence on marketing in the coming years. Knowing what people search for, how they phrase their searches and the sort of volumes involved can be far more useful than the traditional methods of research - plus it's real time and it's free.
As an example look at this;
Yesterday there was a Blackberry service problem in the US - and what do people do when their Blackberry dies? - first they panic, then they turn to Google. 5 of the top 50 searches in Google hot trends yesterday were blackberry related yesterday.
John Battelle called search a database of intentions in his excellent book Search. What is Google saying about your brand?