I've never experienced such a spam infestation of this kind before. If I was a suspicious person, I could almost imagine it being a deliberate attack from, for instance, a recently banned user.
Just turn off new user registrations for a few days. It will hardly be that much of an issue to new legitimate users, as long as a message informs them of the reason.
Looking at the posting frequency, it is automated, constantly 2 sets of 2 posts a minute, then a set of 3 posts a minute.
It looks like it is automated advertising for the developer/owner of the sites involved.
The head lines from the subject pop up in google too.
Its been spamming ubi, battle.net, and several others.