Do I name? Yes and No.
There are several things that I have to take into account....and not just with snakes...I own tortoises too...
Survival. I don't know...it always seems like if I name something right away it doesn't do so well. Well, I've never had this problem with snakes, but I have with frogs and other smaller pets.
The same would go if I had a snake that refused to eat. I think we all know that can be hard, as even when force fed, a snake won't neccessarily survive. Luckily I've never had to worry about that...
Age and gender. I rarely have this problem with snakes, but with other pets such as tortoises, its very hard to sex them until they are pretty old. My only adult russian tort, I bought as a female. Turns out after a few years, he was definitely a male. Suddenly the name Natalia didn't fit very well.
The right name. This might sound wierd, but certain names seem to just 'click' for me. And I often don't name a pet until I find that right name...
Changing a name. I never change names, even if I don't like them. I've adopted a few snakes before and they have the same name the previous owner gave them...it just doesn't seem right to change it.