There are cases where surveys are useful, but none of them hinge on getting accurate results. The two that come to mind: push polls, and exploiting sample bias to make yourself look good.
I've enjoyed the recent 5-hour ENERGY ad about how many doctors approve of their product. A whopping 73% of doctors recommend low calorie energy products... when measuring the percent of those who recommend energy products.
http://www.youtube.com/watch?v=RCqT3fdAAHQ
While there are abusive uses like push polls and leading questions, there are legitimate uses too.