Time and place is key. Swearing is just another tool to express an emotion. A bug report comes in and you find and fix it in 5 minutes, "Hey I fixed that bug, fix is going out." A different bug report comes in that you stay up 24 hours finding and fixing, "Motherfucker! I finally found and fixed that issue that was fucking with our payment system. Have I mentioned that programming is fucking horse shit? I'm going to sleep now."