The surfer isn't as hungry as he used to be. The quick fix solution for paysite owners is to raise the price of trials and memberships. A less educated customer is more of a customer service burden, however, so this increases expenses. If the blow to the wallet is too dramatic then you lose customers. So raising the prices when demand is essentially down is an unwise business practice over the long haul.
Less people patronize the park.
This is what Oz from The Adult Webmaster recently wrote about in his article regarding sponsors reducing payouts on pay per signup models. Tightening the belt, however, can have a negative effect too. If you cut back on webmaster payouts then you will lose webmasters advertising for you. This seems to be a real no-win situation for those that run affiliate programs. Your other options involve cutting corners somewhere in the business and these are murky waters.