They include sites that seem to be their competitors because they earn referral fees when you buy memberships. A couple mentioned in scam forums even try to dupe you into buying the same list at other membership sites they own under different names. Naturally, these sites also have an incentive to exaggerate how much you'll earn from online paid surveys.
A popular and free survey site, Toluna boats more than nine million users across the globe and is well known in the industry, having been running for 17 years. Offering questionnaires for you to fill in to provide leading companies with your opinions, Toluna also runs a range of internal games and schemes, as well as offering product testing to some lucky users who can bag free products.
IOCS is a not-for-profit research organization that conducts studies and experiments on shopping-related behavior – things like how we, as consumers, evaluate products, how we make the buying decisions, etc. Although the focus is mostly on shopping related behavior, some of their experiments and studies include broader areas of marketing, psychology, and economics.