Excellent execution, so the way i understand it, a user burns steem dollars to null account to promote their post only on the promoted section, according to how much they pay for it, then it is free to be organically upvoted from there and rank on other pages. So it is never embedded in any kind of sidebar, and is completely unobtrusive to those who don't want to see it.
Would there be a transparent notice that a post has been promoted on the post itself if it ranks up through the trending page? And would the poster be able to add additional steem dollars to their post after the first injection, to try and outbid other posts for the top spot?
If this works well, it will massively increase the demand for steem based dollars, and reduce their supply, driving their value up.