This happens to me a LOT. What's wrong with me?
It also happens to me in chat rooms. People will be so caught up within their own conversations, that when I try to say hi, no one sees me. I often use a different color font, a brighter more noticable font, and that sometimes works.
This used to happen to me when I was in school, and I think it's because I had the wrong friends, because my last best friend of high school NEVER did that to me! Even when with his own friends, he always included me.