Why are so many people scared of spiders? That's actually a good question. There's something about the 'unfamiliarity' factor - the more different something is, the scarier it is to us, so things with lots of legs (or no legs) or not 'mammal-y' or skittery or web-spinning, etc, etc. tend to be more frightening to people who let themselves get frightened. There's also a lot of learned fear involved, although that partially relates to the last bit - people are more likely to believe scary things about anything they're unfamiliar with; even other people who appear different get this treatment, so it's not surprising that spiders do. A lot of us exaggerate any sort of danger (real or imagined) and start treating all sorts of silly rumors as fact and the next thing you know, there are any number of 'everybody knows' stories which are complete hooey but which people are convinced are true. There may be an ingrained (instinctive, 'pre-programmed') element at work, but that's a hard thing to try to tease out from all the other stuff that governs our behaviors.

I guess the main reason is that we humans tend to save a lot of time and effort by not learning about things, and just lumping all 'possibly dangerous' (eg unfamiliar) things into one 'definitely deadly' category so that we can be really scared without actually having to think about it. It's stupid, but very human. If you want to stop being scared of something, learn about it - that way you understand what the risks (if any) are and can handle them.

Spiders really don't bother me that much, unless its a black widow or a hobo spider. Why are people scared of the non venomous types?

Of course anything with poison is freaky but there are only a few types of venomous spiders