In case you didn't know, here's why.

They send you emails inviting you to take a survey, typically offering two dollar amounts: one "when you qualify and fully complete the survey", and another much lower amount, "if your survey answers do not meet the criteria to fully qualify for the study".

Note how unclear that last statement is. Is it a survey, or a study?
Are they one thing, or two?

That's not an accident.

What happens in practice is this: they ask you a bunch of questions, and as soon as they get an answer they don't like, you are rejected and given the "token" amount (usually $.50).

What they don't tell you is that this could happen even if you've completed most of the survey. So you get $10 if you "fully complete" the survey (meaning, they like your answers), but only four bits if you complete 95% of it -- which, by their own estimate, takes 20-30 minutes.

This is completely unethical, and not just for the survey respondent.
Do the companies paying these scamsters realize how they are operating?
A host of issues are brought into question, from ethics (obviously) to accuracy and respondent selection (not so obvious).

Does anyone know which state(s) have jurisdiction over e-Rewards?