Nerf is great fun! We crack it out and have a round every now and then and it is awesome!

You will never get a definitive answer for your question. It is one of those things that you have to make up your own mind about. Our kids know the differences between toys and real. They know when we are out with the real guns that there is a massive amount of respect and safety involved so no one gets hurt, while they know that nerf is a toy and shooting them is a game and won't hurt anyone.