I can't speak for anyone else, but I had a couple interviewers google me. One pulled up my college athletics profile on his computer during my interview. One found an essay I wrote that got published in our school magazine and commented on it (I never mentioned the essay or anything about in my application). There was nothing bad that they could find, but it definitely got my heart racing when I realized they were definitely looking me up. So...an adcom might not take the time to look you up, but an interviewer definitely might. Better safe than sorry!