24p is often sold as a magical button that will transform video into film. It won't. 24p is merely one small and relatively unimportant part of "The Film Look" and this video graphically presents the definitive argument proving that 24p video doesn't automatically look like film... but it also makes a decisive argument (or two) for shooting 24p anyhow.
* Update: YouTube is distributing HD at a frame rate of 29.97, so that is what you should use for YouTube. But who would do something like that?!