A DigitalPoint Forum thread sprung my interest in locating one of those shopping cart icons near a Google AdWords ad. So far, I have only seen them in screen captures, such as the one posted here. The thread asks, how do I get one of those icons in my listing, of course someone explains that it is from Google Checkout.
The search term that triggers a shopping cart icon in the buy.com ad on the right works for CS50, the thing is, if you are using Safari, you may not see the icon. In Firefox I see it fine, but no matter what I do, it does not appear in Safari. Plus the ad text is slightly different.
Forum discussion at DigitalPoint Forum.