There was a very tragic event in our area (Norther NJ) just recently. A 12 year old girl committed suicide due to bullying, some of which was described as "cyberbullying." There are not a lot of details available yet, so it's hard to say if there was a smartphone involved or not. Can you imagine that not only are you getting bullied on school grounds, but now it also follows you home in your pocket? Egad. No escape. All by yourself. Horrible.
I guess in the end it really is up to the parents to do what they can.