http://www.itworld.com/software/213403/bing-and-yahoo-sponsored-results-lead-hard-remove-rootkit
Yet another genius idea from bad guys - buy ads on popular search engines that lead to pages that install rootkits. According to the article this used to happen to Google but then Google started double-checking all their ads.
A security expert also advises users to type in the web address instead of clicking links. Yeah, good luck with getting people to do that.