I recently watched this wonderful video of a lecture by John Cleese on creativity. Full transcript here. I'd really recommend watching it in its entirety.

Here's a part I particularly enjoyed:

So, here's how to stamp out creativity in the rest of the organization and get a bit of respect going.

One: Allow subordinates no humour, it threatens your self-importance and especially your omniscience. Treat all humour as frivolous or subversive.

Because subversive is, of course, what humour will be in your setup, as it's the only way that people can express their opposition, since (if they express it openly) you're down on them like a ton of bricks.

So let's get this clear: blame humour for the resistance that your way of working creates. Then you don't have to blame your way of working. This is important. And I mean that solemnly. Your dignity is no laughing matter.

During college I was interning at a law firm. I remember the exact moment when I realized this wasn't going to work out for me. We were being shown around the (very large) offices by one of the partners, who commented "During the 60's this building actually used to be a factory". To this I jokingly replied "I guess some things never change!" I was quite proud of myself but apparently this kind of humour was quite taboo. Throughout the rest of the internship I never did quite figure out what type of humour wasn't taboo. I did however figure out that I couldn't function in environments where a sense of humour wasn't valued.

(For more thoughts on humour PG talks about it in the context of good design in his essay Taste for Makers, search for "Good design is often slightly funny").