Absolutely no one makes money off this. Also, their executive staff is in shambles, and their website hasn't been updated for quite awhile.
The tests:
The requirements for the test are so filtered and "screened", you'll be lucky to take a test once a month! If you're a student, well then you don't really get any tests! If you are not full-time employed in exactly the industry they are looking for, you will not make any money, there will be no tests available.
Reviews from their clients:
Usertesting does not statistically improve any market performance of any company, it's a widely known fact that these third-party site testing startups do nothing for a business in the large scheme of things, financially nor brand wise.