Oliver Widder. Used with permission, CC 2.0 Germany.
I take humor very seriously.
That's not to say I don't use it. I use it all over the place. Too much, maybe. But I try to use it strategically. It's a tool. It's for eradicating stress, nullifying hostility, and breaking logjam. It's for revealing possibilities and inspiring creativity.
It's good for a laugh.
Granted, there are appropriate times to be careful not to use humor. Nobody likes a joker at a funeral. The presence of a charismatic leader who's more serious than you is probably a good indicator that it's time to keep the Tom Swifties in the bag. And humor is hell on translating technical documents.
That being said, if I err (even on technical documents), I err on the side David Pogue recommended. We need more humor. Life is uninteresting and sterile enough. Laugh a little, dammit!
C'mon, seriously. I'm not joking.