the problem with pegging would be the transition to it - the value of peoples holdings will be cut. by 70%.
Granted people can move to STEEM, but if they don't already when such an announcement is made it'll crash the price down regardless.
The whole SBD thing is weird in my opinion. everything on Steemit says it's the value of 1 $USD, and all the calculations on the wallet, and even the conversion, seems to work it in that way. They should at least update the front end to reflect today's reality.