"Is the ability to play fast an innate skill or can it be acquired?"

I'm not sure there is such a thing as a truly innate skill. I think the players I've seen who play fast but can still articulate properly are so versed in the subtleties of the instrument and the music it seems effortless, when actually it's taken a lifetime to get to that skill level. Which I guess means anyone who puts the effort in could learn to do it, although whether they would be subject to the same influences that enables them to be as good as they could be is another matter.