Why not offer a competing and potentially superior USD peg token within the ecosystem instead of using something external? Unless I'm wrong, Tether has 10 minute (average, so you could be waiting 30 minutes+ sometimes) confirmation times because it's built on Omni which is built on the Bitcoin blockchain. Steem blocks are 3 seconds apart. Nowhere do I see Tether being advertised as speedy.
It might be a longshot but Steem's SBD has the chance of being a popular and possibly even de facto USD pegged token in the cryptocurrency world as it expands to include more than just computer nerds (in line with the goal of Steem).
I think it is dependent on how many people it brings in. It might be useful to get some more expert economic opinion on this - I wonder if there are any economists in the community who can look at this?