I read in a book some time ago that 24 fps was decided on as the result of a variety of different tests- it was determined that it produced smooth motion but being slightly under 30 the strobing effect put the audience into an altered state. After lots of tests done at a variety of different frame rates, it was determined that 24/25 was the best format for narrative stories.

But hey, maybe I am wrong and maybe 48 fps is great. But judging by the audience reaction to the first 48 fps Hobbit clip, I have a feeling I am not the only one.