Are you friends with your co-workers?

RedHot thought this was worth mentioning said
4

I have a smallish group of friends from the office. We go out drinking after work, we play in a kickball league (non-company), or go shooting or something on the weekends. A lot of the people I know outside of work say they would never be friends with their co-workers for various reasons. I've even been told that its a bad idea (outside of the expected hating their co-workers or the "my co-workers are dumb-asses" reasons). I don't get it. I guess maybe it's because I'm not in a job where we need to step on each other to do well in our careers. Most of us are in different technical fields anyway. Are you friends with anyone you work with?