I wanted to start some sort of affiliate program, and have tried various software, but none "did it for me", and the better options cost too much.
What about just putting on field on my order form that asks the customer where they heard about us? To ensure they answer the question we'll give the customer 10% off there first month bill.
With that problem out of the way, the only other one I foresee, is lack of trust from affiliates. Would you trust a setup like this? Affiliate programs can be manupulated just as easily, but would not having a system to check clicks-thus, sales, etc turn you off? (Of course I would still display sales and commissons online, but none of the extra's that real software could provide.)
I've seen lots of sites that just have a question in their signup form asking who referred the customer. I'm sure the customer will be honest. I doubt the referrer would try to act like a customer and signup for another service he'll have to pay for just to get a commission.
Why don't you write a small PHP/PERL script that posts cookie in user's browser (expires in 60 days) and then put a hidden field in order form that will pull cookie from user's browser if it exists.. there you go