C1. Introduction
The rapid development and pervasiveness of information technology have changed many business practices. Amazon (http://www.amazon.com/) and similar eCommerce sites, where customers buy products and pay for them on the Web, have grown rapidly and become a critical channel for reaching consumers. According to the U.S. Department of Commerce, U.S. eCommerce sales totalled $193.8 billion in 2011, up 15.2% from 2010 and 69.2% from 2006, and accounted for 4.7% of the total retail volume in 2011 [78]. Hence, eCommerce sites, along with traditional brick-and-mortar shops, have received significant attention from academic and business communities.