Fear of Public Speaking

An old friend of mine used to say, "Don't worry about making a fool of yourself, it'll happen soon enough." But we do worry about it. The fear of public speaking regularly ranks along with or above fears of that which could actually cause us harm. Why are we so afraid of it, especially when those whom we heap praise and money upon are those who do it. We want to be actors and singers, yet we find ourselves petrified at the very thing we desire.

Why are we so afraid of public speaking?