This comment was posted to reddit on Jan 25, 2015 at 10:09 am and was deleted within 18 hour(s) and 51 minutes.

Indeed, the pilot wave theories are non-local. That is my point. The idea thumbs its nose at everything special relativity says about causality. It proposes that all the particles in the unvierse are constantly sending each other signals faster than light, well outside the lightcone, arbitrarily far away. These pathologies are merely hand-waved away in the papers about these models. On the other hand, if you assume that quantum mechanics is correct, there are demonstrably no such problems, due to the no-communication theorem. But a classical theory doesn't inhereit this property merely by claiming to describe quantum mechanics in a particular limit. The pilot wave models also all inevitably rely on singling out a preferred reference frame, which is another indication that the whole idea is in deep conflict with relativity.

All of this is in contrast to the fact that taking QM seriously remarkably eliminates all potential problems. A naive but straightforward analysis might tell you that "There's nonlocality, but strictly of the causality-preserving variety", due to the no-communication theorem. But a more comprehensive analysis, particularly where you remember to treat all observers as quantum systems themselves, leads to an even better conclusion, namely, all of the apparent 'non-locality' is an illusion based on unjustified classical assumptions, and the fully quantum description works with *all causal influences propagating strictly into the future lightcone.*

Pilot wave theories are an essentially attempt to undo both of the revolutions of the 20th century, which is understandable from a narrow human intuition standpoint, but the remarkable ability of QM and relativity to solve their own problems makes clear that this is not necessary. And there is certainly no physical evidence indicating we're taking QM or relativity too seriously.