The whitepaper talks about rewards as subjective proof of work:

Subjective Proof of Work presents an alternative approach to distributing a currency that improves upon fully objective Proof of Work systems such as mining. The applications of a currency implementing subjective proof of work are far wider than any objective proof of work system because they can be applied to build a community around any concept that has a sufficiently defined purpose. When individuals join a community they buy into a particular set of beliefs and can vote to reinforce the community values or purpose.

In effect, the criteria by which work is evaluated is completely subjective and its definition lives outside the source code itself. One community may wish to reward artists, another poets, and another comedians. Other communities may choose to reward charitable causes or help advance political agendas.

From the perspective of a taxman this should be pretty much same as Bitcoin mining. An individual is doing something for blockchain, which is then rewarded with cryptocurrency.

There is also very big difference between Steem and Steemit. Steem is the blockchain that is actually making the payments. Steemit is the company that runs this website (steemit.com) which is only a user interface for Steem blockchain. So Steemit is not the one who is controlling directly what happens in the blockchain, although they do have a lot of Steem Power which gives them a lot of voting power.