How much $$

The other day i got this survey in the mail from the AIGA (American Institute for Graphic Arts) asking me to disclose my job title and salary. Paper-clipped on the front of the letter was a one dollar bill. The reason for this survey was to survey design professionals and poll the average salary of different level designers in the industry. I'm sure it would be sorted out into many other subsections that include area of design, geographical location, age, sex etc.... Whatever. Initially I was surprised that they would send cash through the mail, but at the same time thought it was very clever. First of all the dollar caught my attention and stopped me from throwing it in the trash. Second it was very much in line with the whole salary theme. And third, it made me feel guilty that i had to fill out the survey for receiving the dollar.
I haven't filled it out yet and also haven't decided if I will. However, I do believe that knowing the salaries of different positions, including our own, keeps the paychecks competitive. That being said, there is something inside me that is rebelling against this concept. Maybe i feel that their concept is manipulative and along the lines of the familia guilt. If they had just given the reasons for the survey without the dollar i might have been more compelled to fill out the survey, maybe not. Anyway I still haven't decided, but I do have to say that this was the most interesting piece of junk mail i received in a long time.