The eBay affiliate program is in the process of implementing a new pricing structure for Active Confirmed Registered User (ACRU) compensation.
The new pricing scheme will reward affiliates for the amount of quality traffic they drive to eBay advertiser sites.
Initially only affiliates that join the eBay Partner Network on or after August 1st will placed in the new system.
All existing affiliates will remain in the old pricing system until November 1st, at which point all affiliates in the US program will be placed in the value based pricing system.
eBay is phasing this change for existing affiliates so they can have time to look at the data and see how the change will affect them.
More details at http://www.ebaypartnernetworkblog.com/en/news/new-value-based-pricing-for-ebay-us-program/