Somehow I think the saying "Keep your friends close and your enemies closer", is rather terrible advice. Might I advise you keep your enemies either dead or really far away from you. I know it's a novel idea, but I daresay I'd want a good amount of empirical evidence in favor of the way it's currently phrased. I've read enough Sun Tzu to know that better answers "Keep your friends close and your enemies guessing." or "Keep your friends close and your enemies misled."
I don't think the prospect of keeping an eye on somebody should put you close enough to get bit. Also, most of the time having enemies is a bummer. Keep your friends close, and your enemies non-existent. It just sounds like crap advice as it's currently given.