2. There is a big difference between "backstage" and "front stage" norms. In many places, swearing is private meetings is fine, but is unwise when you are being observed front stage. You can see these norms at play if you listen to the amazing tapes made by both Lyndon Johnson and Richard Nixon, as they swore constantly backstage, but not in public. Of course, you have to be careful not to slip, as when George Bush -- who thought the microphone was off -- commented that a New York Times reporter was a "major league asshole" at a campaign rally.
3. Swearing on rare occasions can be very effective for the shock value. If you swear constantly, then people will barely notice it. But when you do it rarely, it can have a big effect. In fact, this phenomenon helped get me interested in The No Asshole Rule. Years ago, at my department at Stanford, one of my colleagues -- who rarely if ever swears at meetings -- had a big impact on our group by arguing that we should not hire a renowned but difficult researcher because we did not want to ruin our group by bringing in "assholes." From then on, the no asshole rule discussed as a hiring criteria. I believe that if he was the kind of guy who swore constantly, we never would have heard it.
4. The norms of the group or organization are crucial. I have worked in some places that if you DON'T swear you are looked upon with suspicion because, well, that is how everyone talks and it you don't swear, it means you are not part of the group. For example, when I was a teenager, my dad owned a company that sold and installed furniture and the like on U.S. Navy ships, and I worked for him now and then. Everyone in the business swore like