Every rabbit has the potential to inflict a very painful bite or to shred human skin with strong legs and sharp claws.  This kind of aggression is, almost always, a last resort after their human failed to recognize earlier communication of displeasure (see Bunny speak 101).

Reasons Buns Bite

• Fear.  A frightened rabbit will lash out at predators who come near in an attempt to inflict enough damage to the pursuer to repel the attack.  These are strong instincts and a frightened bun will not take the time to determine if that hand that is swooping toward them is their beloved owner or a predator.
• Blind Spot.  Rabbits have a blind spot in their vision.  They cannot see directly in front of them.  If you look at a bun's head, the eyes are on the sides, allowing a wider field of vision.  When people stick their hand in a bun's cage, they usually stick their hand toward the bun's head. . . in the blind spot. All the rabbit knows is that, without warning, something has touched them.  They, instinctively lash out.  Always warn your bun before approaching them and, better yet, make sure your hands are not in their blind spot.
• Pecking Order.  Rabbits in colonies develop very strict hierarchies.  Much of this is achieved non-violently, but nips are frequently part of establishing who's in charge.  If your bun feels that you are trying to get "too big for your britches," they may bite you to remind you that they are, indeed, in charge.
• Sexual Behavior.  Nipping is often part of the mating ritual.   So, if little Pookie is circling your feet and nipping ankles and hands, consider yourself "wooed."
• Pain and Illness.  Rabbits in physical distress will bite.  Any sick or injured animal is dangerous and should be approached as such.  Sick and injured animals should always be handled with gloves and towels.
• Strangers in the Warren.  If a stranger attempts to be too familiar too quickly, then Thump may nip a finger in warning.  Rabbits love the familiar and they often require time to accept change.  This includes new people in their lives.

In many of the cases where people have been bitten, frankly they have deserved it.  Children who harass the cute little bunnies in the cage by sticking their fingers in the bun's face over and over deserve a little nip.

Other related links:

Who Wants a Mean Rabbit?

What do I do with my mean bunny?