Dan is allowing that the steem dollar may not absolutely equal "1 US dollar worth of steem". There is the the canadian dollar, the australian dollar, and maybe we can allow the Steem Dollar, as a distinct unit of account. To address the second black swan event. We could have it redeemable for: 12 Japanese Yen, 2 rmb, 0.3 dollars, and 0.3 euros worth of steem. So we have mitigated the effect of US dollar inflation. We need only for the witnesses to modify their price feed of the Steem Dollar, if that is what the blockchain settlement logic uses.