That's actually one of the worst things you can do to a dog. Tying them up will produce an unhappy, unsocialized, and mean dog. A fenced yard, electric or otherwise, is a better solution. I work for the local H.S. and have seen dogs tied up for basically ever. Collars embeded into their necks, no fresh water avail, no shelter. Makes me sick.
People who want to own dogs need to be responsible for them. Teach them obedience and care for them properly or just don't have one.
As for what may have happened to someone walking by...you can see in the video this was a game for that dog. His fur was not raised, his tail was wagging, he was not attacking so much as playing tug-o-war. Just with a very large chew toy.
