I like dogs. But I want to point out that dog attacks are a significant cause of human deaths caused by animals.

Everybody has mentioned poor socialization, but nobody has mentioned dogs attacking a human (esp a child) because it is desperate for water or food. It happens.

When my niece was three, she was attacked by a neighbor's dog that had been chained outside on a hot day. The dog was desperate for water. The police were called, and the neighbor got the point. My niece, now 40, still has scars on her face.