I occasionally carry one or two golf clubs on board a flight. Before I tried it, I called the airline (United, I think it was) and they said up to 3 golf clubs was acceptable as carry-on, but 4 or more must be checked. They seemed more concerned about overhead space than security.

I find it peculiar that they think you could hijack a plane with a baseball bat, but not with a 5-iron. Of course, I was on a domestic flight, not an international one.