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.
Return on Time – Is it an hour of your life for $2.00 or truly a fifteen minute survey? We find out if the Return on Time (similar to Return on Investment) pans out. Surely, some will be better than others for not wasting yours. Basically, we've evaluated not only how much you actually get paid to take surveys but also how long it takes to earn that cash
Valued Opinions – Decent site with reasonable surveys ($2 for a 20 min survey). Everyone is annoyed by this site because they tacked on a $2 few to the Amazon $20 gift card and $5 to the $20 Visa gift card so it costs $22 to get the $20 Amazon and $25 to get the $20 Visa. They claim its because of extra fees they incur. I dunno. Also, it can take weeks to get credited for a survey which is frustrating.