So I signed up and payed $5 for a 1,000 visits to my site. It said they had completed my order and showed a list of sites where visits came from. I then looked at Google Analytics and it showed zero hits. So don't waste your money. It is too bad.
They are not scam. As a member i've been paid almost $300 in total. As an advertiser i don't believe they scam you. You might contact them. And GA won't register every visit. Check your server logs for actual traffic details.
I was not paid yet as a member but they are a reputable ptc site. As stated you can check Google analytics for the real score of your site's hits.