I'm actually happy to give people answers to surveys - but only if I've got the time. Because in some cases is does improves service. And you can usually tell from the survey pretty quickly.
Biggest clue is time taken. If the survey says it takes 2 minutes, and you hit question 10 and it still says 1% done - then you know it's all bollocks.
Or if you get one on the usablity of a website and the second question isn't about page loading times or menu placements but asks "how did your interaction with our animation style make you feel? 1. Emporwered; 2. Awesome; 3. Soaring like an eagle; 4. Fantabuloso; etc...
So I close the survey as soon as I come to a question that I can't understand or that's written in such obvious marketing bullshit that I know the answers are going to be transcribed into an unreadable graph on a powerpoint slide to be shown at a training meeting in Hell's boardroom.