There was an interesting article on search behaviour from a study released in the last United States Summer.  Here are a few statistical examples given in an article with the link to the article provided below:

 three out of four (72 percent) Americans report experiencing a degree of "search engine fatigue" (i.e., they're regularly becoming frustrated during searches) and wishing they had a more comprehensive and quick way to find the information they're looking for online.

This was among the key findings of a survey of 1,001 representative U.S. internet users jointly conducted by Kelton Research and Autobytel Inc. last summer. The frustration was even more pronounced among 18- to 34-year-olds, with 23 percent of these younger internet users saying they "always" or "usually" experience search engine fatigue.

Getting beyond the top-line results of the survey, consider this: 64.5 percent of survey-takers say they've spent more than two hours in a single sitting searching for information on search engines; 37 percent have spent three-plus hours and nearly 5 percent have spent seven or more hours -- more or less a full day of work -- searching for information on the internet in a single sitting. So, it should come as no surprise that 75 percent of those who experience search engine fatigue report that they walk away from their computers without the information they were originally looking for either "always," "usually" or "sometimes."

The link:  http://www.imediaconnection.com/content/17855.asp

It is very interesting and I am sure many of us see ourselves in these stats with increasing frustration of not finding what we want despite targeted search terms used and geographical filters applied.

This provides one of the great challenges the search engines have to sift through the billions of pages of data to find through artificial intelligence what is on the searchers mind itself.