I think there have been to create marketplaces but for various reasons they didn’t gain much traction or the website costs became preventative. I think the dropping of the Steem price made things unworkable.
But I can easily see there being Etsy style stores springing up, or at least a “pay by Steem” button attached to websites.
There really is no limit to this stuff.
I love hearing about use cases for Steem. One time I took a photo of a McDonald’s Hot Fudge Sundae and asked people to upvote it to see if it would pay for itself. The price of Steem had jumped to like $0.40US (it was a while ago)and it returned 3 fold.
I do know that people advertise their home-based businesses on Steem, and I am starting to see my own account as something of a brand. It needs a design overhaul, sure, but I want it to be an account you can trust and that both FIAT and Steem flow freely through it.
RE: Blockchain business...It's a thing