I once heard a variation on it (don't know who originated it, but must have been a business shark), which goes like this: 'Keep your friends distant, keep your enemies close, and keep your worst enemies closest'.
Some people think the quote comes from interpretations of Machiavelli's work. (The first great political philosopher of the Renaissance. Florence, Italy. 1469-1527).
The way i see it this quote is a general proverb. It could have been said by anyone. Possibly the politicla genius of Otto von Bismark who often was friendly to enemies (Austria) or perhaps Al Capone. It was a wise man indeed though. And he knew that some people just shoulnt be trusted.