eBay and the United States Postal Service have a long relationship thanks to the importance of shipping to online sellers. In fact, eBay with its 120 million active users (globally) is one of the U.S. Postal Service's largest package mailers. The Postmaster General was warmly welcomed by eBay sellers when he appeared on stage at the 2005 eBay Live conference. But it's only now, in 2013, that the USPS is opening a store on eBay.