Not sure which of these categories I'd fall into, but backstopper might be the closer fit. As far as I understood, the value of SBD is secured by the ability to trade it for approx $1 worth of STEEM at any time. So speculators can speculate the price to the moon, and anyone holding SBD will benefit ... but at the end of the day, each coin is really just an IOU for the STEEM equivalent of $1.