9 of 10 people who want dogs for guarding need them big and furious. The important thing they forget is dogs can attack on anybody, including their owners if not trained.
Let me narrate u a incident from my own experience. Some years back I had the same mentality. My dog Rocky, a Great Dane (60 kgs and 35 inches) was deadly ferocious. He wasn't born so but I made him such by telling him to charge on every live thing. Under me he was sort of under control and never bit anyone and also he was a working dog, protecting and guarding our fence was his job, so no one complained. During those days I used to stay at Hostel and ocasionally came home, so our worker took care of him.
It was Holi that day and I returned home at around 5, in the afternoon. I saw blood on the stair-cases till my room on the first floor. The dog had actually dragged a guy( around 6 feet and 80 kgs ), who was an acquaintance at our house. I learned that the dog was free and this guy entered the house wearing a helmet. This incident had occurred just 15 mins before my return and my family had taken him to the hospital. At the hospital people queried had any wolf or tiger implicated these wounds. There were around 15 - 20 scars, 1 or more inch deep at places. This was 7 years back, now after several surgeries he has some feel in his left hand. I am grateful to him that he did not take me to court.
Later the same people who loved him (Rocky) hated or feared him. I managed to relocate him at a farm outside the city but he had several issues there too, including killing a cow. He lived upto 5 years old and died more of neglection than anything else as no one dared to enter the cage and treat him.
Who is the culprit the dog or me?