Having a third party send an email that includes a link to a survey to your advertisers with no warning is not the best way to get advertisers to complete your survey. The problem from the advertiser perspective is is that this message could be from anyone. When the sending email address and the site the survey is on are unfamiliar, why should I risk filling it out? How do I know its not a competitor who obtained my email setting up this survey to gather competitve intelligence?
I have no problems filling out a survey, and I'm pretty sure that this survey request is legitimately from a company working with Yahoo!. But I still won't fill it out because there is always a slight chance that it is not. Please do something to show that these are legit survey from Yahoo Search Marketing and I will gladly provide you with helpful feedback.
I fill out surveys all the time for Google and MS, but never when they come unannounced with nothing to show that they are legitimately partnering with a trusted source.