I am scared of small fast snakes(garters, racers) while big giants don't freak me out one bit.

I originally thought that it had to do with how you were raised, if you were raised to be scared, then you would be but I realized that wasn't the point. My parents were both raised to scared of snakes but I am a total addict. I can't figure out what it is. Is there any reason why some people are afraid of spiders? I know of a Trant. lady who has an arachnaphobic(sp?) daughter, how would that come to be?
Great idea for a thread