I'd like to see one of these gain some traction!
But I also wonder; would Steemit society work for online auctions?
If there was a Sell Your Stuff community, and you could post to it without it showing up in your main blog (new feature idea?) then we could have a blog, and separately use Steemit for sharing music, and selling crap around the house.. it seems to me a major sticking point, and probably something communities can or should address.

So then someone does a deal, with another steemer, and then if it goes south; there are many witnesses... we have a blockchain and it really would be perfect for this sort of thing. Holding the escrow, until item is received, and then purchaser agrees to receipt and funds are released, or not. Worst case, an arbitration board has to decide if there is intent to defraud, and release funds to the seller, if item is not returned.