This Topic has been touched on by multiple users but here's my take on the situation with my limited knowledge.
From what I understand, we're getting paid for posting content right? Well, if you're getting paid for posting someone else's content then that content has been copyrighted; fundamentally so. That IS illegal.
"But Steemit isn't a currency", sure it isn't, and you're right, kind of...
Steem and Steem Based Dollars are taxable commodities, which become classed as donations/payments whenever you receive precious Steem Power and/or Steem Based Dollars. In other words, you are being paid just by receiving something of value!
The fact that you're being paid Steem Based "Dollars" for posting someone else's content should be enough to scare you away from doing it.
I've done a brief read over of the Terms Of Service provided by Steemit, and not a single copyright clause covers any of us individual users in the case of a potential violation of Plagiarism/Copyright. Steemit however is covered under these Terms of Service.
Even I am guilty (purging myself for your benefit here). I posted a Youtube Video of "Black Man loves Pokemon" which I didn't create. Thankfully it didn't start trending. If it did and I were to have acquired a payout, I could've incurred a potential lawsuit from the content's creator. (I could be sued just for "trying" to make money off of another person's content)
We need to keep this information in mind when we post someone else's content.
We first need consent from the original Creator of any content. Otherwise, you are setting yourself up to go to court over the money you may or may not have made.
When it comes to photos and images, the same could be said again.
Know this next time you post someone else's intellectual creations
This has been another public service announcement from your friendly neighborhood Sensei
