I used User Testing for about 18 months and I used to make a regular £20-30 a week from them, tests were interesting and insightful, some were short and some involved a one on one interview which were higher paying. My rating on the site was 4.5 out of 5 after doing 301 tests and earning £3000, so all was good until at the end of December I stopped receiving any invites. I got in touch with User Testing but they sent me an automated response which did not answer any of my questions. I tried again and received the same response. In the end I gave up and cancelled my account as from looking at other reviews the same thing seems to happen to lots of people using the site. Its a shame they cannot give you a proper response to why they have stopped sending you tests.