They don’t give a reason for this, but I assume it has to do with taxes. You see, if you pay someone $600 in any given year, you are required by law to report that earning and send them a tax form at the end of the year. And since 60,000 equals to $600, I assume they have that rule in place so they don’t have to deal with all that paperwork come tax time.
The concept of data mining and profiting off that data mining isn't anything new. And while some companies engage in some rather disreputable practices to do this, Global Test Market seems to be doing just fine with the whole “consent to disclose” thing. More importantly, in some cases this may help you as some companies will offer to do more specialized product testing once they've identified you as their target demographic.
Playing games online: if you like playing games, why not turn the hobby into a moneymaking activity? There are tons of websites out there that reward their loyal fan base with points when the complete a game or play for a certain amount of time. These points can then be exchanged for real money. Sites are able to do this by sharing the profit they make from ads as an incentive for users to visit the site.
Paid survey site companies invest billions of dollars into marketing research online. They always want to find out more intricate details of a consumer's relationship with their product. Whether it's a new television show or just an existing product line, companies like Disney, Samsung, and Sony go to great lengths to find out their ideal audiences.