It is understood that chained dogs are at risk for attacks by wolves, other dogs, moose and abuse by people. It is also true that chained dogs are dangerous to people. According to the Journal of the American Veterinary Medical Association, 17 percent of dogs involved in fatal attacks on humans were restrained on their owner's property. These dogs are not allowed the normal "flight" response when chained, often leading them to fight instead.
A chained dog often lacks socialization and human interaction, essential for any dog's mental health. Chained dogs are frustrated by isolation, lack of exercise and boredom. Additionally, they must eat, sleep, defecate and urinate in the same small area, which is unnatural and creates more problems with house training. These dogs become neurotic from their situations, further deterring human interaction.
I have a wonderful dog (now 13) who spent the first two years of his life chained to a tree. The owners gave him to me willingly, although they warned me what a terrible dog he was: fights with other dogs, not house trained, ran away. These issues were related to his circumstances; we started daily walks and he lives happily with other dogs.
I implore you to take another look at your neighbor's barking, lonely dog. Consider talking to owners of neglected dogs and working to make their lives better.
-- Metis Riley