It is very common for advetising company paying to get opinions from consumers of all kinds of people because they need it.  If company produce products or provide services that do not meet the consumers' needs and standard, who is going to give them business then?  So it makes sense. 

Actually they used to conduct focus group and pay for the participants before internet time.  And comment form, feedback form is the free way to get opinion but did you ever fill in one?  Yes, may be one or two but the rate is very low because motivation is near zero.  And motivation is so weak that the design of those form must be short and simple, then how can you get the real and in-depth information?!

I guess you got the big picture here but still, there are a lot of things you have to be aware of.  Internet is super convenient, handy and useful but it is also super dangerous, horrible and scary!  I must be exaggerating but somehow it is true.

So I am here to share my experience and get you start more easier and have a peace of mind.  First of all, do your research online before taking action on anything.  In your research, you will find tons of website and information about pay to do survey.  And I do a lot of research also, this is my summary.

1) Don't pay for anything unless you are sure the site is trustworthy and worth for.  Usually advertising company do not ask for money because your opinion is priceless to them, how come they ask you for money and pay you back later???  Don't make sense at all.  But there are survey data company (like a middleman), they gather lots of survey company and even advertising company, they recruit members and do the matching for both sides.  And they usually ask for fees from both sides, kind of administration fee.  If you do not want to go through the trouble to do the searching yourself, you can pay for these services.  But for me, I do not buy the concept of paying to get the job, so I do the hard work myself.

2) No matter you are paying or not, you have to do research.  Surf around the web for feedback of the good and honest site which is the real deal.  Some of them never has survey to fill in, some of them never pay a dime, and a lot more tricks to go.  So do your homework!