I walked with a friend in her neighborhood this afternoon. This was my first experience seeing an invisible fence in action. This yellow lab wanted to either play or attack -- I couldn't tell which -- but the electric charge of the invisible fence stopped him cold. It was rather disconcerting for both of us.
It looks like a playful warning. Sort of like, "This is my house! Do you want to play? This is my house! Do you want to play?!" Cute! But, yes, that would be a strange feeling to stand there and watch him bark at you and only go so far.