SEOdisco has screenshots of Yahoo! asking for feedback on the organic, natural, free search results, asking the user.
How useful are the first two results below?
The survey gives you a 1 to 5 point scale, 1 being not useful and 5 being useful.
We reported something similar in the past, but they seemed to have referred to rating PPC ads at Yahoo!. After looking back at the survey, which asked people to rate the first five results, maybe it wasn't rating the sponsored results, maybe it was rating the organic results.
We know Google constantly asks people to rate the sponsored results with a "Yes" or "No" response to "Was this link useful?"
SEOdisco posted this information at WebmasterWorld message number 3143964.