I know a pretty heavy user of that site and when it first emerged, some were making thousands USD (in the Steem currency) when others upvoted their posts (though there's a slightly convoluted method/timeline for accessing all earnings).

Anyway, the amounts have since slowed, but it's still a pretty active community. There are, however, quite a few schemes around some version of paying people to upvote posts, which is surprisingly allowed. Overall, it's an interesting concept but seems unsustainable over the long-term.