Scammers, lazy posters, plagiarists, slackers, cheap effort contributors... they all make money in the short term. NONE of them make great money in the long term.
Maybe they make money in the short term, but not much. Unless they're circle jerkers. Even then though, it doesn't last. I saw that kind of behavior kill Epinions.com back during the dotcom bubble.
Long term, probably few people will make great money (other than whales who bought in early), but I think that a surprisingly large number of people may well make decent money, a good supplemental income. I am convinced that Steemit has immense potential.