This chapter is intended to describe as plainly as possible what Google AdWords actually are and how they fit into the typical user’s journey in a given online search session. … In the effort to master the finer points, it’s easy to lose sight of the basics of how and why people are using Google Search, and what you can realistically expect them to do when they come across your ad. It’s also easy to make stereotypical assumptions that there is one way of searching the Web, or one typical model for making sales to online audiences. …
From search to buy: How real people use Google. For millions of Internet users, search is a habitual activity, performed daily. According to recent figures from comScore Networks, the average U.S. user performs 35 searches per month. The average Canadian user is a bit more active, at 40 searches per month. Keep in mind that these are averages; many users search much more frequently than that.
http://www.dmnews.com/pdffiles/chapterthree.pdf
