I would never do it.
A friend of mine down the road does hers, and says she can't keep chickens without them cannibalizing each other. When I told her I was getting chicks, she said to me, "You'll want to come borrow this, then." and took me into her laundry room to show me her new debeaking machine. I don't know why she has a problem...her chickens are not really overcrowded or anything.
I do not debeak my chickens, nor do I disbud (take the horns off of) my baby goats--instead I give the chickens enough room and food, and train the goats to not touch anyone with their horns. I can't bring myself to mutilate them just for my own convenience, when other management methods work better. I wouldn't dock the tails off of dogs or draft horses, either.