Is this new?
I can’t say I’ve seen it before.
A “Was This Link Useful?” prompt, with Yes/No buttons, appeared when I clicked back from a search result. This is not on Adwords listings, this is on the main organic SERPs.
It is clearly a voting mechanism testing the relevance of search result listings. The voting buttons appear, Web 2.0-stylee, as an animated drop down under the link you clicked, once you visit the site and click the back button.