If you'd like to try this surveygizmo out for yourself, go to Questia and try to win an 80GB iPod by taking their survey. It's actually fun to complete, and the mechanism couldn't be smoother, or less aggravating.
A. Voit, S. Mayer, V. Schwind, and N. Henze. Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems, page 507:1--507:12. New York, NY, USA, ACM, (2019)