The first days when starting an offer with pay-per-click site were totally happy for everyone, when they haven't verified your site yet, but when they finshed, maybe the bid would increase, and they started to supervise your site, it's hard to get money from them. And i think when people visit your site, if they know ppc, they will never click on your site, certainly, anyone still has a little selfishness, they don't want you to earn money from their clicks.