comScore released a study on the relationship between paid search marketing and retail e-commerce, based on the March 2007 comScore qSearch Marketer report. The study revealed that e-commerce sites are the most frequent users of search engine marketing, with each of the top ten search engine marketers being either retail or comparison shopping sites. In March, nearly 20 billion sponsored links were served to U.S. Internet users from the top search engines, with eBay.com leading the charge as the top search engine marketer with 802 million sponsored link exposures.