Here's the latest thing Facebook has thrown at it's members to try and apparently cut down on networking and making new friends?
I managed to get this while trying to send a friend request to a celebrity (a guitarist in an 80's band) who has over 4,400 friends, so this person obviously doesn't mind adding as many "strangers" as possible, (and probably wants to). But Facebook, in it's infinite wisdom, has chosen to punish people anyone who does this.
So, this was triggered when clicking on the "Add Friend" button on a person's profile, getting the "Do you know this person" dialog box, closing it, and clicking it again.
First, it logs you out, requiring you to log back in. You then get taken to a "Friend Requests Blocked" page with a button you HAVE to click saying to "Proceed". Note that logging back out, clearing cookies, and logging back in won't make it go away. Then next screen shows you this (Fig-1):