Meritline recently sent me an e-mail asking me to fill out a survey. The e-mail stated that Meritline would send me a desktop organizer for free as a reward. I chose not fill out the survey.
The irony is that I might well have decided to fill out the survey had they not offered any sort of reward. I thought, "I don't want a desktop organizer, so why should I bother filling out the survey?" Had they not offered a reward, I might have thought, "If this survey is short, I'd be happy to answer questions to help improve Meritline's services."
Survey incentives not only pale in comparison to the deterrent effect of a long survey, but they can actually make some potential respondents less likely to complete the survey.
Furthermore, isn't Meritline biasing their sample in favor of people who want a desktop organizer?