Narcissistic Personality Disorder and Borderline Personality Disorder - two interesting diagnoses from the DSM-IV and subjects always fraught with controversy. One well written and acerbic blog that often touches on these issues, the Last Psychiatrist, has some interesting posts analyzing the new narcissism and also writing about borderline with an excerpt below.
This is why narcissists marry borderlines, and not other narcisstists. Two narcissists simply can't get along: who is the main character? Meanwhile, two borderlines can't be with each other-- who supplies the identity? The narcissist thrives with the borderline because she provides for him the validation that he is, in fact, the lead; the borderline thrives with the narcissist because he defines her. And, as she will tell you every single time, without fail: "you don't know him like I do." Everyone else judges his behavior; but the borderline is judging his version of himself that she has accepted.
More reading from the LP on the diagnosis of borderline.