The difference is being not paid and paid. Just joking... well sort of joking. I'm always a little cautious with the "lead" programs because there are many different ideas of what is a lead and they are all subject to the advertisers interpretation. I have an account with ClickXchange and yet I do wonder about their ablility to track leads and sales. I try to stay to only clicks with them. At least, everyone knows what a click is and it has least ability for an advertiser to cheat.