I met Jack, a very large red Doberman, and his people, John and Melanie when Jack was 11 months old. They live in the Tri-Valley area of the Bay Area. By the time I met him, Jack weighed nearly 80 pounds and had bitten two people. The last person he bit was John's uncle who happened to be one of my favorite teachers growing up at Wood Middle School in Alameda. Small world!
People have asked me if I'm afraid of dogs, and while I can't really say that I'm afraid of them, I can say that I have a very healthy respect for them and what they are capable of, especially a dog the size of Jack. This respect may be the reason that in 20 years of dog training, I've only been bitten one time, and that was during a consultation. I've never been bitten by a dog that I was working with on a leash. (Knock on wood!)
I spoke to John and Melanie extensively by phone before we met and learned that Jack was quite territorial around his house, so knowing this history, I asked them to have him on a leash when I came over the first time. When I went to the door, I heard what sounded like a 180lb dog bark and charge the door. I stepped back and John opened the door with Jack on the leash. Jack was barking and pulling to get to me so hard that John could hardly hold him back. They ended up on the front porch and I ended up having to step back about 20 feet to keep from being bitten.
I had John hold Jack and I went out to the sidewalk because I wanted to encounter him away from his home as well, and when Jack saw me he would bark, show teeth and lunge at me. He was so strong that if I held my ground he would eventually be able to pull John towards me and get to me. Pretty intimidating.
I remembered that I had talked to Melanie by phone when Jack was about 6 months old, but for whatever reason they decided to try a few other things to help him. These days, there's lots of information available about dog training from books, to the internet, to television shows that show miracles that happen in 60 minutes on a weekly basis, delivered by a trainer who for some reason unknown to me, seems to have no problem being bitten.
Much of the information that is available, however, if not all of it, seems to fall in what I call the "cafeteria style" training. In other words, for every behavioral issue, there's a remedy. "If the dog does this, do that"… "When this happens, respond by doing that"…
I don't work this way, but take a more holistic approach and work to establish boundaries and a relationship between a dog and its people that is consistent and clear 100% of the time… not just the few minutes a day that is spent "training". We did this with Jack, and between this, and teaching John and Melanie solid handling skills, he began to respond immediately. 
I just met with Jack and his family, which is about to grow by one, last night in a park where a little league game was ending. We stood and talked while parents, kids and pets all walked by and Jack sat nicely by their side, completely non-reactive. John and Melanie's guests can be comfortable when they visit, and in a few months when they have their first baby, they are confident that Jack will be fine with the situation.
Thanks to John and Melanie's consistent follow-through and their willingness to trust in my experience and knowledge, Jack knows jack!!