To kick things off, the simple act of friending someone on Facebook does not give them control over your account. They do gain a little more access to your information, but not much more. By information we mean posts, list of friends, pictures etc. Someone that is your friend on Facebook could conceivably spam your friends with garbage posts and friend requests, but they cannot simply take over their accounts.
No, this one is just an annoyance as you get to tell everyone that sends one of these warnings to you that it is fake. Interestingly enough it is not all that new either. The dire warnings of a dangerous social media account have been pushed before. Either because the person is question is a hacker, or because they are a scammer/ thief etc. These pop up from time to time and most people do not bother to do any real research before they start spreading things around (much like any headline they read).
I guess the moral of this story is; be careful who you add to your friends list in the first place and take a couple of minutes to confirm what you repost or spam your friends with. It will save us all some time and help out when there are real threats to talk about.