I don't really know, but I think there could be a problem if the person can point to enough details to say, "That's me, and you owe me." I'm sure there's plenty of lawyers that would jump on it if you made money with the story. If you don't make money with the story, there's not much for a lawyer to go after, and that's their bottom line. Or I suppose a person could sue you for libel if they say it's untrue. I'd ask a lawyer if I were you if think those problems could arise. Or look on legal forums elsewhere, I'm sure it's been asked before.