By Diane Bartz WASHINGTON (Reuters) – The growing online usage of ads designed to blend in with the rest of a websites content, a practice known as native advertising, may be illegal in some instances, the Federal Trade Commission warned on Wednesday. The FTC said that a survey of online publishers found that 73 percent allowed native advertising, the digital descendent of the newspaper advertorial and televisions infomercials. Marketers have … moved past the banner ad into advertising that is more seamlessly, and inconspicuously, integrated into digital content, FTC Chairwoman Edith Ramirez said in a speech that opened a conference on Blurred Lines: Advertising or Content. While native advertising may certainly bring some benefits to consumers, it has to be done lawfully, she said. By presenting ads that resemble editorial content, an advertiser risks implying, deceptively, that the information comes from a non-biased source. The website Buzzfeed.com is often cited as an effective user of native advertising.