In the beginning of my career, certainly before I had the cash reserves to easily weather being laid off, I worked for a company that had a 4-month death march. The two nights before the work was due I literally didn't sleep. As an aside, I really can't recommend this; the code I produced was basically nonsensical. And I think I added far more bugs than I removed, but I did get the final blocking bug out (no matter how many every-so-slightly lower priority bugs I added in its stead.) The ceo came in the morning of the final due date and saw me -- wearing the same clothes for nearly 48 hours and utterly sleep deprived -- and made a crack about how I didn't look like I'm been working hard and I should get to work or he'd fire me. Joking about firing people may or may not ever be funny, but definitely stops being funny when the person has the ability to do it. And some managers fail to understand that - your relationships with employees change when you're their supervisor.
Similarly, it's really not hard to see how being too close or too friendly with people you supervise can cause all sorts of problems, ranging from letting them get away with things they shouldn't because of the friendship or them sharing things with you that force you, as a boss, to choose between your friendship or what your company requires.
I just don't think it's a good idea either way. It's a bummer that it makes workplaces a little more impersonal, but imo it's for the best. I bet it's the reason the military doesn't (from my perspective) seem to encourage enlisted and officers to co-socialize.
