We are almost to the point where an entity like Facebook or Amazon could do controlled economic experiments.  Or they could gather so much data, that when filtering them based on the experimental criteria, whatever remains could show a significant result.<p>Aside from the <i>technical possibility</i> of doing economic experiments, there is also the <i>ethics</i> of doing them.  You are not only involving humans, but doing so on a grand scale.  To prove a point, you would not only need to possibly send an economy into a recession, but you would have to do so dozens of times to get significant results.  The people you are experimenting upon might get a little murdery.