(Edit: Fixed the typos :-)
I'm massively bullish on Steem right now. I think this is going to explode but not because loads of people are posting snooze articles or pictures of themselves in bikinis in order to catch the attention of one of the founders or a whale investor.
I've searched for this idea and cannot find anything explicit, only implicit comments about third party apps and subchains, so here is my contribution to the market of ideas.
Steem could be truly revolutionary for the web, and I have put down my top-ten, in no particular order, medium term use cases for Steem. Please correct me if I am fundamentally misunderstanding what is feasible & not to build on top of Steem.
Yelp Killer - why are we posting & curating inane chatter? Why not rate and review local restaurants or businesses? Restaurant reviewing used to be an actual job, why not again? A wholely unpaid online activity is local reviews and this entire market can be commercialised.
SkyScanner Killer - bots are used to pull airline prices into comparison sites like SkyScanner, but for this website to make any money they need to actually process the booking, a massively complex challenge that requires enormous investment and was completely dependent upon the airlines allowing them to integrate with their booking systems. What if a new Steem-based SkyScanner website allowed third party bots to pull flight details and prices in, thereby creating the content for people to browse. By upvoting the good results users would be rewarding themselves, the bot creators, the website itself and helping the next people to come along to find flights. The website would get paid in Steem so they wouldn't have the expense of processing the booking.
SteemBooking.com - why do you book your hotel directly through booking.com? Booking.com don't want you to... They just want to get paid and the only way they guarantee getting paid is by processing the booking. But what if the website could get paid in Steem. Users could create bots to check for capacity at hotels and other users would have incentives to come back and review their experiences. This website would very quickly build up the highest quality reviews.
SteemAmazon.com - OK, this is pretty ambitious, but think about it for a second. What if you could go to a website that has the highest quality book reviews and buy your books directly through the platform. Amazon reviews are useful, but Steem makes them incentivised to the point of being a core USP. And that goes for every product on Amazon. Smartphone comparisons and reviews? Reviews of homeware brands? All incentivised, all high quality, why would you shop anywhere else?
SteemEtsy.com - are you a maker? Do you want to give etsy a cut of 10% of your sale? Does quality really make it to the front page of etsy or is it just those who advertise the most? What if SteemEtsy.com made money from the amount of posts and upvotes relative to the rest of the steem network rather than living off advertising and processing payments?
SteemTrades - I want a tradesman, but I can't find any reviews online. Why? Because there is no incentive to review or rate a tradesman. The job is done, you forget about him. So local tradesmen websites are no better than traditional classifieds. But if there was an incentive, and a further incentive for others to validate my review... That changes the game. The value of my review or my upvote is directly correlated with the quality of the tradesman and I am paid for it. The more jobs he gets the higher his reputation, the more valuable is my review. That review can keep posting for years.
SteemInsurance.com - I've never used a comparison website for insurance before, but if I did I'd want to use the one with the highest quality results and the best reviews. Plus the website would have a revenue model finally that didn't require payment processing.
SteemAirbnb/CouchSurfing - Airbnb grew out of the simple fact that Couchsurfing failed to develop a viable revenue model. But what if they could have generated income from the people rating and reviewing other members? Airbnb may not exist now if that had happened. On top of that, the same argument as above on booking.com applies to Airbnb.
SteemStackOverflow - over 50% of software developers in the west are on StackOverflow. It's a massive success story that cracked technical Q&A. Financial incentives for Q&A never worked because financial tech online was so unsophisticated. The code for Stack Overflow is open sourced, spawning many engineering & science based Q&A sites. Why not augment them with financial incentives? Developers in the Philippines could make a living by supporting developers in the west, rather than simply building reputation.
SteemQuora - why stop at engineering Q&A? Why not take on general Q&A? Questions about philosophy or problems in your love life? Welcome to subjective proof of work baby!
Bonus: 11) SteemTwitter - we all know Twitter is in trouble. Jack Dorsey's return has failed to produce a viable long term revenue model after a year and investors are getting really impatient. What happens when the plug is pulled and Twitter faces an existential threat? Will they do something radical? Why not try integrating Steem? Is that feasible? Possibly a layer on top to augment the existing platform which could eventually take over as the default Twitter interface, where individuals get paid for quality contributions.
Edit: a few more use cases I forgot to mention address charitable funding and crowd funding for the arts or popular projects. It's an exciting time to be involved in crypto!
Another that came into my head is event guides. It's very difficult to find accurate, continuously updated & charged event guides with rich data. This has been a massive challenge because the incentive structures for contributing accurately have never been there. Steem be the game changer this area has been looking for!