I've done it to a few people before. Two were past relationships, because it was just too awkward to talk to them after the relationship broke off. I have a hard time with being able to mentally put what happened behind me and just talk to them as people. The other two were because they did something rude and disrespectful to me. One of them was a childhood friend who started lashing out at me last year or so for not seeing my grandmother while she was sick and dying. He accused me of being things that I'm not and didn't seem to make up his mind about whether he should forgive my actions or continue to persecute me. The reason I didn't see her was because she was the other person I shut out. ^^ Not that she'd done anything terrible to me, I just got so tired of her guilt tripping me every single time I talked to her. Not at all a nice thing to do, but I loved my grandmother and I didn't want to end up saying terribly cold and hurtful things to her when I finally broke.