One of mine mainly did this to my stepson, whether he was coming or going. She wasn't being playful, I would almost think fearful whenever he would move. We worked at giving her treats whenever he entered, and when he was leaving, I would do 'Ah Ah' to interupt her. She also started this with my DH. We had just adopted her ... she is 2 years old, and prefered women to men. My DH won her over with crackers. We have since adopted another 2 year old female, so she is no longer the 'new' dog, and I think she feels a bit more confident. Now all four mug whoever comes in the door. I can't say I've seen any more biting for at least a month now...
I knew we had it beat when DS fell asleep in the recliner and she walked up to his hand (which he left dangling over the armrest) and stuck her head under his hand like she wanted him to pet her. So cute... but her look of disappointment when he didn't respond was heartbreaking...