So far reading through this thread, NO ONE seems to want to point out that every dog can inherit a different temperament based upon the dogs that they were bred from.
I'm not talking about breed here. I'm talking about the individual dog's attitude and personality. My wife and I have three Shih tzus and while two of them are very children friendly, one of them will snap and bite if not monitored closely (He is the alpha male among the three).
My ex-gf at one point had 14 dogs - 4 Dutch Shepherds and 10 Malinois (Police dog training rejects from Holland). She had pedigree papers on each one and they were kept in separate run areas in groups that matched their personalities. A few of them were straight-up dog killers, but were as gentle as can be with people. Others didn't like people at all and even we had to be careful in handling them - Even though they would obey commands, they still had to be watched as their personality was too volatile.
Any dog can be dangerous even despite training. It is up to the owner to know a dog's personality as well as possible since the parameters change completely in some instances when a dog senses fear or is faced with what they perceive to be a weaker member of the "pack" (in most cases, children).