What causes phobias?

I think phobias are usually developed in the child hood:

*due to some incidents
or
* the general upbringing. (I know a number of ppl scared of cats, merely 'cause their Mums were scared of cats and never allowed one in the house!)

Perhaps the ppl with phobias would be able to tell better
(which brings us to another poll: how many of us out there are suffering from some particular phobia, and why?)

Pin~Jinx /anarchist

The primary cause of agoraphobia is panic attack associated with panic disorder. Approximately 40% of people with panic disorder develop agoraphobia.
The cause of social phobia is unknown. There is a possibility that altered function of serotonin (a neurotransmitter involved in many behaviors) may be a factor.
A frightening or threatening experience with an animal or in a particular situation can cause a specific phobia. For instance, someone who has been bitten by a vicious dog may generalize their fear to include all dogs, regardless of the animals' dispositions.
Fear can be learned from others as well. For instance, the child of a parent who responds with intense fear and anxiety whenever they encounter a harmless garden snake learns to respond to snakes with the same fear and anxiety.
Source:
http://www.mentalhealthchannel.net/phobias/causes.shtml

I have arachniphobia (fear of spiders) and I know exactly when it started, and why:

I was very young, perhaps four when my parents came home one day from getting groceries. My mother gave me a sack to carry to the house. Half way there I got curious and looked inside - there was a live lobster. I dropped it and ran shrieking. I'm not afraid of lobsters, just spiders, and I don't really fear them, I just hate them.

Catty (too many legs)