[Simon]

I think the reason it's rare is that with CCBill's system you have to open two separate accounts with each sponsor to promote both the pay-per-sale and the partnership programs. You can merge them so that it's only one login to see the stats for both accounts, but it's a bit of a hassle none the less. CashFetish uses CCBill and does offer both programs, but only a handful of webmasters have ever taken the time to sign up to promote both of them.