Originally Posted by Grey

I'll step in to point out (as I always do ) that this isn't really accurate. Ken G is correct that there is no way for us to use quantum entanglement to send messages that violate causality, or anything of that sort. However, Bell's theorem demonstrates that, for the results to be consistent with the predictions of quantum mechanics and observation, the whatever underlying mechanism determines the result at A must take into account information about the choice of measurement at B, which can be arbitrarily far away, and can be outside the light cone (past or future) of measurement A. It does not require ascribing any reality at all to the electron's wave function, or treating it as anything more than a bookkeeping technique to come to that conclusion.