This the second time I received such. First time was two dollars, I think, a kind of research. Seeing how hard they were trying, I mailed in the survey after taking away the $2 attached in the envelope.
Now, I get $5 cash (is this related to the last mail, I have no clue as it happened a while back, although I recall something about a promise of $5 continuation survey back then). This one is from Nielsen Media Research, 150 N. Martingale Road, Schaumburg, IL 60173, Attn: Juan Carlos Avila.
Again I mailed in my survey, which asked about TV viewing habit. I didn't give them my phone number, putting down the obvious 000-0000, too many spammers these days.
I would say I have the right to just take the money without sending in anything, because it may seem to be a trust issue, but consequently, it is a kind of investment in human supporters. One does not need to comply another's deal simply because the other dumps a load of papers in one's house.