Later cameras, like my D3X and D800E have greater MP counts and some-
thing like my D3S is working very fast. In both cases, the sheer amount of
info, through size and speed respectively, will fill the camera's buffer that
will need a very fast "write rate" to the cards.
All this is based on the assumption that, like me, you think that the next shot
is the best one and I should, at anytime, be ready for it.