… if it’s worth the effort, this TPM hack may nicely complement an Evil Jan attack. First the attacker carries out the Evil Jan attack to obtain any user-provided key material, next he takes the machine away and cracks the TPM for the rest of the key material. Usually there are easier ways after the initial step, but if, for whichever reason, they should become infeasible, going for the TPM might be an option.
Leaving the TPM exposed to physical attacks while protecting the RAM of a system from wire access, DMA, and cold boot attacks would be a pretty stupid design error, though. But who knows?