I completely believe in karma. And yes, karma can be a b@#$%.
A couple years ago I found out that a good friend of mine from back home (I was living in Kansas at the time, but home was Nebraska) had just broken up with his girlfriend. She had moved from Pennsylvania to be with him and when he left her she pretty much just stayed with some friends she had made in the year she'd lived there with him. I never got to know her that well, but after talking to her for a little while she seemed like a pretty good person to be with. Needless to say we got together and I had a very good few months with her. Well the people she was living with felt she should move on with her life and suggested that since we were so good together that I find a place for her with me in Kansas. So I talked it over with her and with a guy I worked with and made an arrangement to be roommates on an apartment since none of us could afford one by ourselves. I was just about the happiest guy alive since this would be the first girlfriend in almost 5 years that would actually live near me.
3 days after we moved into his apartment (He had just gotten a divorce and needed help to pay rent) I wake up out of a dead sleep with the feeling of something being wrong. I went into the living room to find his head in her lap with her playing with his hair. I didn't know it at the time, but had I came in just 10 minutes sooner, I would have seen something far more shocking. The weekend before she moved down I took him up to meet her in Nebraska and apparently they started talking to each other over the phone right away. There was nothing wrong with my relationship with her. For whatever reason she decided she would rather try a relationship with someone she had just met than with someone who she's heard from everyone who knows me, that I'm a great person.
Needless to say I was crushed. But I didn't get nearly as mad as everyone thought I would. I even gave her the opportunity to redeem herself. She then proceeded to manipulate me in an attempt to get me to drive her back to Pennsylvania. About a week later I gave up on her for good. And that was when karma struck her. She wound up pregnant with his child. He turned out to be an abusive, over-protective boyfriend. I had no idea he'd be like that. But I guess that was his way of dealing with his cheating ex-wife. (I actually became fairly good friends with his ex after this

)
Shortly after I broke up with her, I met my wife. She has got to be the absolute greatest thing to happen to me. She takes care of me like none other

And I won't take any day with her for granted.
I feel that that was the good karma of not going nuts and beating the crap out of my ex or the guy who decided to cheat on me (with me in the next room no less!)
So yeah, I really feel that karma is quite real.
-C