Lacie did it when she was a puppy, but not as an adult.

It is actually quite common.

A couple things to try: Teach your dog to always greet visitors with a toy in her mouth. That way she is somewhat distracted. Also, tell your visitors to ignore her completely for the first five to ten minutes or so that they are there. No talking to her, no making eye contact, no touching her. After she is calm, then they can pet her. This teaches her that she will rewarded with attention only when she is calm.