Thanks for your answer... So I guess I should put some limits on how much one referal fees for a month and pay only accounts that stay active more than a month.

Thanks for your answer... So I guess I should put some limits on how much one referal fees for a month and pay only accounts that stay active more than a month... I hadn't thought about limiting to student email addresses... but that should limit the possibility of fraud. I'm also limiting customers to only one country too (malaysia)...