My experience doesn't seem all that unusual. I spent about a year clicking links in their emails, taking 30 minute preliminary surveys that told me I didn't qualify for a full survey, and slowly building up a balance of around $70. When I submitted a request for a check, I got an email stating that my check would be held because they wanted to be sure I would continue to participate. Funny thing, they didn't send me any more emails so I COULD participate. Naturally, I never got my $70.
I held up my end of the deal. They don't have the class to hold up their end of the deal. Don't waste your time with these spam scammers.