There will always be problems with those companies. But i have few things to say about surveys. This companies have some rules how you have to completed surveys. Sometimes people have a message after half a survey that they are not qualified. I've done hundreds maybe even thousands surveys over the years not only on WGT. As we all know surveys are boring and its complete waste of time and we want only a reward for them as fast as we can. It is one of the mistakes, surveys need to be complete slowly eg. when you have simple questions, age etc, don't click- next- next- next fast. Their systems can detect that people don't read questions carefully (even if you can read fast and mark answers immediately - don't do it), it is possibility that program will throw you out of the study. Next thing, between random screens they putting questions, where you have to select the correct answer suggested by them- control questions. Again to check if you read all.
In the end, few tips how to be qualified more often to the studies. It's simple- you need to lie. I found out that they are looking most times for 26-32 aged people with high income from big cities.
Simple thoughts but it might be helpful for someone.
Cheers