I used to have anxiety in crowds too, panic would set in and a fog would roll over my senses. Doesn't happen much anymore.
I always thought it was a self-esteem issue, and the panic I felt further enforced my pathetic opinion of myself.
I guess I kinda grew out of it, getting married and having kids helped.
Like some of you guys, I'm learning that the anxiety was and is a symptom of something greater.