I used to have problems speaking in front of a large crowd, but I had to get over it. It took a while, but now I have given talks in front of 200 people, I present on a weekly basis to a board of directors, and I attend weekly networking events. The weirdest thing about it is that I'm an engineer. I liken it to training a dog. If you never socialize it, the dog will always feel insecure around other humans/animals. For me at least, social anxiety is an experience thing.