Who cares, because eventually the buck stops somewhere. In other words, it doesn't matter how many layers of simulations there are, because at the top presumably there's a "reality". It's easiest to just assume that's where we're at, but if not, all the questions we ask about the nature of reality/life/being are still just as valid (even if we're operating at some remove from it).
Why need there be a top layer? Certainly it meshes with our evolution provided common sense but what makes it necessarily true? Some philosophy that abhors a completed infinity?
