YouGov / They refuse to respond
At the end of the Yougov/CNN panel survey I did on August 16, 2007, the screen said that I would be credited with a $10.00 Amazon.com voucher; this is what the original email announcing the survey also said. I did not receive the voucher. Repeated emails to Yougov were totally ignored. Eventually, on October 1, 2007, by dint of persistent emails, I did get the voucher which I was promised three months before.
On July 12, 2008, I received an email announcing another survey. When I logged in, my CNN Panel account said "You have not completed any surveys." As a matter of fact, I have done several surveys and accumulated hundreds of points. As usual, all of my emails to various Yougov addresses have been ignored. From what I have seen on various Internet forums, neither the this fraud by Yougov nor their refusal to respond to emails are isolated cases. Their fraud is habitual.