Danger! Beware of Dog!

As the stranger enters a country store, he spots a sign: "Danger! Beware of Dog!" Inside, he sees a harmless old hound asleep in the middle of the floor.
"Is that the dog we're supposed to beware of?" he asks the owner.
"That's him," comes the reply.
"He doesn't look dangerous to me. Why would you post that sign?"
"Before I posted that sign, people kept tripping over him."