Arguments

Ever had an argument with somebody where you got into a phase proving him wrong but he would in no way acknowledge that he even might be wrong?
Or better yet, ever run into the opposite situation where you where clearly proven wrong and wouldn't acknowledge that?
I occassionally run into the former. And I'm not talking about those cases where 2 people simply have different opinions and both think the others opinion sucks.
I'm talking about situations where you can prove the other wrong. I observed that behavioural pattern fairly often. Seriously, whats the deal? Is it damaging peoples ego if they have to admit being wrong? I observed several patterns when it became obvious that one was wrong:
- Denial without further arguments: "No, you're wrong, I'm right"
- Ad hominem attacks: "If you weren't an idiot you'd see that I'm right"
- Silence
So for those lonesome readers that have somehow stranded here - what's your opinion? Why do people behave that way? What are your experiences?
That's all for today, only the questions. Maybe on another day I'll have some possible answers.