Not all Google traffic is made the same - some sources send tons of clicks, some send highly converting clicks, and rarely the twain shall meet. 

Sometimes, you find the strangest things when you don't expect them.  Case in point: in November, we were looking into some statistics for Google traffic through our ad network (Chitika), and found that people who click the "Google Search" button on Google's homepage are fifty percent more likely to go on to click an advertisement than people who use any other method of executing a Google search (including people who hit the enter key on the same Google homepage).  Now, these people only account for 12% of our network's Google traffic, but I was taken aback that such a minor difference in the method that people use to perform the same search made such a huge difference in what they did post-search.

I contacted Rand Fishkin about this, and his response was blunt and to the point: "Sophistication is my guess - hitting enter... likely indicates a more tech-savvy (and hence, click-sensitive) individual."  So with this in mind - tech-savviness being inversely proportional to advertising clicks - I decided to take a look at another Google search method, the Google Suggest function.

Punch a few letters into the search box at google.com, and the search engine will pop down a list of what it thinks you're searching for - for this example, I entered "seo" into the box, and got suggestions ranging from "seo tips" to "seoul national university."   Where your site falls on this list determines how much traffic you get from it (duh), but it also determines the ad clickthrough rate of the traffic it sends to your site.

15% of all traffic from the Google homepage comes from Google's suggest function, and the further down the suggestion chain you go, the better your traffic converts.  So, when we look at our example of suggestions for "seo", we see this:

Based on network-wide statistics, SEOmoz should see a very small portion of their Google homepage traffic (0.67%) coming from the suggestion, but if SEOmoz ran ads, this traffic should click on them at a 1.58% rate. 

An interesting statistic, and while it may support the idea that less tech-savvy people are more likely to click ads, you can also interpret the findings to say that people with more general searches are more likely to be open to suggestion.  Where you want to end up on the suggestions list depends on what you want to gain from it - you can use it as a driver of a decent amount of traffic, or to drive a small amount of more highly converting traffic.