Wild and out of control dogs. This is one of the biggest reasons I get called in. The dog is jumping, barking, pawing, running around like crazy. The more it provides this behavior the more frustrated the human gets, often yelling and pushing the dog away.
How does the dog see this behavior?
Yelling = barking. "Yay, we are both barking out of excitement! I have accomplished my purpose!"
Pushing away = game playing. "Woo hoo! I jump or puppy nip at you, you push me away, I have your attention so I jump again! What a great game we are playing!"
The dog is desperately trying to get your attention and in his mind, ANY attention is good attention. He has gotten you to interact with him. What we do with training is adjust our communication so that we are asking for the behaviors we want and the dog learns what behaviors nets him this positive attention. Then we end up with a calm, well mannered dog who you want to spend time with.