I have to think it's marketing on two levels;

1). to get more people to click ads (for the reason you describe), and;

2). to encourage others to advertise, (as in -- "See how many clicks you're missing").

In regards to non-techies -- yes, and I can't believe how many of them I talk to, (potential web dev customers), and when I walk them through a search and mention listings at the top of the page and right column are ads, many say they didn't know that...

I don't know that I want my competitors knowing how many clicks I've been getting or how many I've paid for over the years.

I definitely think that it would encourage buyers to click on heavily clicked on ads. There is a reliability factor there as well.

Interesting test and I see positives and negatives depending on which side of the tracks you're on.

Would this not be some sort of extension to the +1 button but for the PPC side?

Google is really an advertising company. Just like all other media like radio, TV, newspaper. Their product is not the entertainment or the news. Their product is advertising. So anything they can do to increase that, the better for them. Google is no different.

So potential positive for Google in getting more people to click those ads and getting more advertisers.

But as Tropical Island points out, do we want competitors to know? Maybe a small price to pay to increase our own clicks.

While I agree that many are not aware that those are ads, there are those who know and refrain from clicking them at all. Others I've talked to don't click the side ads, only those above the SERPs.

Also, seems this might affect newer advertisers negatively. If I just started a campaign and a competitor started a year ago, he'd have more clicks. Would searchers be more inclined to click on his ad than mine, even with a better offer? Maybe a better system would be "x% of people liked this ad". I doubt Google would do that since they don't want advertisers to know how individual competitors are doing.

Another thing, too, is that clicks from search or including the content network?

what does nextag's aggregate click volume have to do with a better user experience for a specific search?

ranking reflects ctr for the search. add a past 24 hour heat meter (marked in % IS) if you think consumers don't understand that the ranking already reflects who's getting clicks for the particular search.

I'm thinking it could change the heat map for the SERP page.. even if only slightly, it gives users "something else" to read/think about in the right column.

Another thing, too, is that clicks from search or including the content network?

There are a number of values that the click count could reflect:
Time frame: daily , weekly, monthly, for the life of that ad?
Data source: That specific search term only? For all search terms where that ad appears? For all instances, meaning SERPs + content, where the ad appears?
Data displayed at start of program: does the displayed click count start at "0": when the program is launched? Or, will it include historical data?