SBD is not really pegged to USD but in reality it is 'half-pegged'.
I mentioned this, saying SBD is pegged from below and explaining that buying it below $1 is a sure gain on your investment (bar massive market fluctuations during the 3 day SBD --> STEEM conversion).
Steem can't 'print' SBDs, it's a fixed supply.
That is not the case. The Steem blockchain prints SBD at a rate proportional to the value of STEEM. As we have just seem a massive rise in the value of STEEM, the rate at which SBD is generated has gone up a lot too.
I have kept up to date with other articles, including those. I agree that the main reason for the rise in SBD value is the scarcity - that scarcity is now dropping. The only way SBD value can rise unchecked is if the STEEM value stays very low in relative terms.
One of the primary jobs of the Steem witnesses is setting the SBD-STEEM price correlation, and they can also implement a bias there to reduce or increase SBD production. For now, SBD is treated as $1 in rewards, so my analysis holds.