bells inequality - How can we be sure that nature isn't "faking" quantum statistics?

In a recent publication, Experimentally Faking the Violation of Bell’s Inequalities (Gerhardt 2011) (arXiv version), the statistics of quantum mechanics is faked using classical light sources. But if it is possible for physicists to fake an experiment to imitate QM, how can we be sure that nature doesn't do the same trick on us? Can it be that QM is a fake, and in the end QM turns out to be an artifact of our imperfect measurement devices?

Answer

I'm not sure it makes sense to ask if Nature is "imitating" Quantum Mechanics.

Quantum mechanics is a mathematical model that gives predictions that are in excellent, well so far perfect, agreement with what we actually see.

I guess the question is whether QM is just a good approximation to the real world or whether it's an exact description of the real world. We'll never be able to prove it's an exact description, but someday someone may find an experiment where QM gives the wrong answers. If so this would prove it's just an excellent approximation.