Content is the king, as they say, and we are now experimenting with the idea that it may be a directy supply for currency. So, let's ask to what other fields can we apply the same ideas:

Music

This is the most obvious one - people love music, need music and are paying for music. It could work exactly like SteemIt, though infrastructure problems may be more demanding.

Games

This is less obvious one. Games provide tremendous value today though, as more and more people enjoy them and can't imagine living without them. Would it work with STEEM model?

Politics

I've been thinking about the idea of virtual country and applying STEEM model to politics could be one of the needed building blocks. So, imagine that ideas regarding law, economics, social issues and other "serious things" working under this model directly. Wouldn't it be more democratic than anything before? I don't know the details required to make it really work, but it's some food for thought.

Software

Bigger and smaller apps, useful scripts and libraries - probably would require two different chains for consumers and developers.

Education

While education may be just a subcategory of story-writing, I'd see it constrained by some structural requirements (courses, curricula, teachers and schools).

I believe many great things will be born in near future based on blockchain technology and how we use both Bitcoin, Steem, and other pioneering inventions that shift more and more power from the corporate and government giants into our hands.