I think ultimately it will take human involvement to fully control plagiarism. Some aspects of checking for it could be automated, but in the end it really should be a human being making a decision. I think that this site should have clear policies about what kind of sharing of other people's stuff is allowed and how it's to be done.

I know, for example, that YouTube videos register views regardless of where the viewer watched the video (directly on YouTube or embedded on someone's blog). For something like this, then embedding another's video ends up benefiting both parties. The one who uploaded the YouTube video gets views, and the blogger gets a cool video to share.

Where it gets more dicey is when it's someone's image and the way to share it on Steemit is to first download the image to your own system, then upload it to a server such as SteemIMG, and then share it. In that process you lose the built-in link to the original material and so therefore there needs to be proper attribution.

But the dilemma doesn't stop there. What if I posted a photograph on my blog (in my pre-steemit days), and someone here took the picture and shared it here and made a boatload of money off doing so. Maybe they attributed it properly to me and put in a link to my blog. Maybe that got me some traffic. But is it still fair? Later on I join the Steemit party and I try to share that same picture but all the people who would upvote it are like "already seen it" and so I can't make money here off my own work because someone else shared it first. That may not be illegal and may not be plagiarism, but is it right? That's where I think it is prudent to err on the side of caution here. I have no problem with sticking to original content because writing is what I do. I can also take my own pictures if a picture is all I want to share. If I'm going to use an open source picture, then I still wouldn't just share the picture; I'd use it to enhance my own work (my writing) so that if I benefit monetarily from it, it's not just me benefiting from someone else's picture, but benefiting from my own work which happened to use that picture.

I guess my point is that when you start getting paid to share content, and what you're sharing is not yours but you're not doing anything that people on Facebook and Twitter don't do, you have to consider the issue of lost potential earnings for the original creator before you go off and just post their stuff and get tons of Steem because your post was heavily upvoted on this platform.