That's the thing---he's such a sweet dog, and most people he does this with see that he is just delighted to be in their presence. I don't actually want to squelch this, as it's one of his happiest, most animated moments. At the same time, I can't let him get into the habit of throwing himself at strangers. I'm trying to put him on a sit stay, then ask the neighbor if they'd like to pet him, wait a beat and then release him. Ideally, he would then walk up politely rather than fling himself, but, well, he's only 3!