The corporate industries are the worst culprits for plagiarism of course, but steemit is attracting scammers. as there's dollars to be made. Well actually, you wouldn't think so going by the amount my photos earn on average in rewards, hahaha, but actually that's a lot of money in some countries and in some circumstances of extreme poverty when you add them up over a period of time. The problem is that they're robbing all good photographers all of the time, in the sense that it is due to this scamming that prevents curies and more powerful voters from supporting photography as much as other creative content, as they need to feel absolutely certain without any doubt that the person posting the photograph actually did take it. It's not that this can't be done, but if you have to go through a process everytime a photograph stood out as being a good one, you can imagine how much of a hassle that would be.
I believe there will be one way or another of resolving this problem to a large extent in the future, it's still early days at steemit. :)