I often check out what is going on with Steem and Steemit on twitter and I happen to come across this tweet and its follow up tweet yesterday. I am sure you can look it up on twitter to find out more information as far as who it is from etc.
More than a month has elapsed since I sent the first of several DMCA notices regarding 30-ish of my copyrighted images being monetized on your site. You have not responded to any. I will escalate to lawyers this week if you continue to duck resolution."
"Update: 
Which are irrelevant, since I have no service agreement with them."
This brings up some points that I think will eventually go through the court rooms a few times. I have no idea if this particular person will escalate it to an actual lawsuit but I know in the future someone eventually will.
It is going to be very interesting when those do start to occur because of the nature of the blockchain and who/what the courts will rule as responsible. I hope Steemit inc has a plan in place already and strong lawyers because this type of thing is coming. Once big companies like Disney/whoever start to get involved in due time this will be taken to a new level. Many of these blockchain uses are somewhat new but the problems they bring up are very old.
I for one don't have full faith that legal systems will work out what is best in these scenarios so I think it will be an interesting thing to watch. Hopefully its not too detrimental to projects but I could see some things getting ugly.
I don't know of any cases in courts now with such a thing but I would be curious if you do and to hear your thoughts on the issue.