The results you quote are very interesting and answer questions I've been worrying about for some time. Apologies for bringing up two purely technical inquiries:

1. Could you provide a reference for the result you quote? You referred to Eq. (34) in Everett's original paper in another comment, but this doesn't seem to make the link to the VNM axioms and decision theory.

2. <<If we have a pair of entangled particles and a classical phone line, I can send you an exact quantum state - it's called quantum teleportation, and it's sweet. But if one of our particles leaks even the tiniest bit, even if we just end up with three particles entangled instead of two, our ability to transmit quantum states is gone completely.>>

That seems wrong to me. There has to be a formulation of the form if the two initially perfectly entangled particles get only slightly entangled with other particles, then quantum teleportation still works with high fidelity / a high probability of success -- otherwise quantum teleportation wouldn't be feasible in reality.