Absolutely email... I hadn't heard anything from my top choice and was starting to get antsy (today marks 1 month since my interview and I had heard nothing). So, I emailed my POI to follow up from the interview. I was then told by another faculty member that I had been wait listed and that he was more interested in taking me on as a student than my POI had been (on my personal statement I had actually listed 3 potential POIs and was assigned to interview with one that, apparently, was not a good fit). I told him I would definitely be interested in working with him and his research is more like what I'm currently doing anyway.
So, the moral of the story is that by emailing someone, not only did I 1) get news that I would not have gotten otherwise, but I also may have 2) improved my chances of getting in overall by hearing from a faculty member that is more interested and communicating reciprocal interest. Really, I can't imagine it would hurt to email. The worst it does is show that you're interested enough to hassle them. As other posters said, just be sure to be polite!