The discussions/debates about individual professional liability insurance on this board always focus on a nurse's (admittedly slim) chances of being included in a malpractice suit, but there's more to the issue than that. Most nursing professional liability insurance policies include coverage for legal representation if you're called before the BON for any sort of disciplinary action against your license -- you're much more likely to find yourself in that situation at some point in your career than you are to be sued for malpractice. Also, many (most?) policies include coverage for legal representation if you're called to be deposed or testify as a witness in a malpractice suit.
If you choose to "go bareback" (without your own insurance) because you just don't think insurance is necessary as a nurse, period, that's certainly your choice to make and I'm not going to try to change your mind. However, if you are not buying your own coverage because you believe that you are protected by your employer's insurance, I urge you to think again!
I've worked for several years as a hospital surveyor/investigator for my state and the Feds, and I cannot tell you how many times I have personally witnessed hospitals/facilities attempt to avoid responsibility/liability for a bad outcome (suspicious patient death, serious injury, etc.), either in terms of getting cited by the state or Feds for deficient practice or in terms of a potential lawsuit by patient/family members, by scapegoating a particular nurse (who, often, hadn't done anything worse than just be the RN who happened to be caring for that patient on that shift) and, as a pre-emptive and self-protective gesture, promptly firing her/him. If you were to find yourself in that unfortunate situation, 1) the moment the hospital blames and fires you, you're no longer covered under their policy, and 2) no insurance company on earth will sell you a policy to cover you for an event/incident that has already occurred -- so you, as the nurse, are left out in the cold, completely on your own. If you do end up needing an attorney for any reason connected to the incident, whether it's being named in a suit, having to go before the BON (guess what else the hospital does at the same time they fire you, to reinforce their claim that you're a BAD NURSE and it (whatever "it" was) was all your fault????), or just being called as a witness in a case against the physician and/or hospital, you're going to have to pay for that person out of your own pocket, and just the first hour of consultation will cost you more than the annual premium for your own coverage would have ...
For me, it's a no-brainer -- best $100 (roughly) I spend every year. My father, a physician, advised me 'way back when I was in nursing school to never think about practicing without my own liability coverage, and everything I've seen over the >20 years I've been in nursing has just reinforced for me the wisdom of that advice.