A report by Reuters says that around one of every five Internet display ads in the United States is now being viewed on a social networking website, such as MySpace and Facebook. The data comes from a new survey by comScore which demonstrates the increasing importance of social media sites and the broadening acceptance of such sites by brand advertisers, as well as the challenge now being faced by the more traditional online publishers, such as Yahoo and AOL.

The new report says that social media sites represented just over 21% of U.S. Internet display ads in July, with MySpace and Facebook accounting for more than 80% of those ads. However, the question will remain as to whether these sites can be used as effectively for advertising, due to the nature of their usage. Also, because the content on social media sites is created by users, some have questioned the willingness of marketers to place their brands alongside that content and the potential risks that could bring.