eBay's ProStores service will close the public beta testing of its Pay-Per-Sale (PPS) advertising program on December 29, 2008. Instead, the company will work with a smaller group of merchants in a private beta test. In a letter to sellers the day after Christmas, ProStores said it had selected private beta participants based on various criteria that the company wanted to test, including record of successful sales, product inventory and store design. ProStores stated that it hoped to offer the PPS Marketing feature to a larger number of ProStores merchants in the coming months.