What is wrong with the De Broglie–Bohm theory a.k.a "Causal Interpretation" of quantum theory? 
Possible Duplicate:
Why do people still talk about bohmian mechanics/hidden variables 

I've heard of De Broglie–Bohm theory a.k.a causal interpretation of quantum theory. The predictions match accurately with with the nondeterministic quantum theory.
As a philosophy buff this one seems just like the classical universe. No funny new-age religion style gimmicks.
So why don't people use this interpretation instead of the Copenhagen "magic" interpretation?
P.S. I'm not an expert. I possess only superficial knowledge of quantum physics.
 A: First, it is a mistake to think that DBB theory is classical. Momenta and positions are still not simultaneously defined, Heiseinberg's uncertainty principle still holds. Second, DBB theory only clarifies the Copenhagen interpretation by providing it with an ontology. A couple of reasons why it is not liked: 


*

*It's thought to be cheap, i.e. the way positions are added to complete the theory.

*It's non-local, while most people argue that quantum mechanics is local.


Here is one of the latest extensive threads about the subject which in the end got closed because it was too argumentative.
A: So why don't people use this interpretation instead of the Copenhagen "magic" interpretation?
People don't use this interpretation, because it is not useful.  On the experimental front it doesn't aid in prediction of experiments, and on the theoretical front it doesn't aid in advancing theoretical techniques or understanding of newly found phenomenology.
A fundamental assumption of Bohmian mechanics is that the unknown particle position when we do an experiment, has an ensemble probability density the same as that predicted by the wavefunction in the usual interpretation.  This is necessary for Bohmian mechanics to reproduce the Copenhagen approach.  So even in Bohmian mechanics, the results for experiments can only be given probabilistically, and the wavefunction encodes these probabilities.  So when calculating experimental predictions, adding additional pieces to the state function do not help, and just are not useful.
Even if we wanted to calculate using Bohmian mechanics, even some simple things become quite needlessly complicated.  For example even if you somehow knew the particle positions and the wavefunction, you still wouldn't know how to update the positions unless you somehow also knew what coordinate system is defining the absolute simultaneity ... and of course this frame isn't measureable.  And even if you knew this as well somehow, things like spin are now not clearly defined.  Spin in Bohmian mechanics is purely contextual, which means to predict the outcome of an experiment (even if you knew all the things previously mentioned) you'd now need to know precise details of the entire measuring device and simulate that as well.  So it should be clear why people use the simpler calculational interpretations instead of Bohmian mechanics.
Furthermore, it has not been useful in advancing our knowledge.  Bohmian mechanics comes from ordinary non-relativistic quantum mechanics.  A large portion of our advances in theoretical physics have come from understanding how to appropriately use and apply non-trivial symmetries.  For example Lorentz symmetry allows us to use certain representation for particles, and also allows many terms in a general Lagrangian to be thrown out.  Bohmian mechanics instead obscures this right from the start.
Instead of bringing us the spin-statistics theorem, or advancing to relativistic quantum mechanics and to quantum field theory, Bohmian mechanics confuses instead of clarifying.  To keep it up to date with current understanding, people would need to keep updating it and playing 'catch-up'.
Some people find it interesting to try to answer 'is this possible?' type questions by trying to find if Bohmian mechanics can be adjusted or fixed to somehow create a Bohmian quantum field theory.  I have yet to see a convincing relativistic formulation.  It is a bit worrisome that there are also researchers (who publish at least, so its not complete fringe) that instead feel Bohmian mechanics gives the correct picture.  At some point it often crosses into metaphysics.  So physicists also tend to avoid Bohmian mechanics, as dicussions of it can often become controversial but rarely ever useful.
