Yes, from what I've read the "blockchain" is considered permanent, I believe because it's decentralized, meaning what's on here is on all sorts of computers all over the place. What's done instead of removal here is that posts can be voted down to the point that they're almost hidden, and there's a note that says that, the post was hidden due to downvotes.
I agree there is a problem here. I think many people don't understand copyright law well and are also used to things being shared across the internet, such as memes. On Twitter you retweet, and on Facebook you can share, and other people's work goes through your account. Then some use can be considered "fair use," creating memes and what not. Clips are taken from videos and put in new videos, and GIFs are meant to be shared. There's a culture of "borrowing" and "sharing" online. But agreed that can only go so far.
You are so right. This is not Facebook! Even a lot of that sharing is actually illegal, but it has become hard to track down the original abuser of the work. I think Steemit should make a huge issue about this, so that people know what they are doing on here! With some people it is definitely ignorance, but with others it's outright dishonesty! Sadly, everyone is going to lose if there is a lawsuit, so they art hurting the whole community!
I've been concerned about that too here. I hope we see more done about it, especially in educating people. People taking content from elsewhere just isn't good for making quality posts. And yes, eventually, given that there are some large payouts here, Steemit could see lawsuits as the site grows more popular.