The campaign to pressure advertisers to leave conservative Rush Limbaugh’s radio show after his misogynistic comments about a college student looks familiar – it was presaged six years ago in a similar effort directed at a San Francisco talk-radio station by an anonymous blogger called Spocko. Since then, contacting advertisers about the content their ads pay for has become routine, fueled by the Internet. This time, organizations such as Ultra Violet, an online activism site focused on women’s issues, are leading the backlash.