Interesting point you brought up about kittens, it seems like no matter where a kitten comes from, for the most part they are tamed fairly easily. It is quite fascinating, because just a few months later, this would not be possible.

Onto the point of reptiles, I think that it all depends on the animal. I have been fairly lucky and had all relatively "nice" snakes, and have not have to put too much work into them. Although I am still hook training my retic, just to be safe. This has been said already, but I do not think that you can breed for a temperment like you can breed for color or pattern. I think that some reptiles are just innately more friendly then others, and I think with proper training and such that a reptile's temperment can be altered.