What is a genuine request for survey participants?

whydoibother?

I know this section is mostly for people looking for survey participants, but it's the most appropriate I could find. I come at this from the opposite point of view. I am someone who has signed up to quite a few market research agencies. They take your basic details and contact you if you are the right profile for one of their surveys. I never make it, but what I have noticed is that I first have to answer about 20 or 30 questions "to determine if I am suitable" to go forward for the paid research. This is after they have been given my gender, age, occupation ... all the basic stuff. The questions are extremely specific relating to particular brands and my views on comparing them. In fact it is suspiciously close to what I would have thought was a market research survey . Basically, do you think all these preliminary questions are necessary, or is it a scam, are they just doing their research for free. Don't get me wrong, I don't see anything wrong with asking someone for their views for free, but I do believe people should be upfront about it if that is what they are doing.