That's the hyperbolic headline. The more tame one: Facebook rolls out an app people may or may not use. It's an app called Messenger that serves much the same function as the chat feature on the Facebook site but as a stand alone app. You can send messages to your Friends, include pictures, include location. It's free and it's available on iPhone and Android, where it is quickly topping the charts. So essentially what we have is free unlimited texting. If your Friend has the app, they'll get a push notification of your message. If they don't have it, they'll get it as a text message or as a message the next time they go to Facebook.
This might be no big deal, people might not want to deal with another app in their lives, people might not want to give this power to Facebook. Also it's only on smart phones, although one could imagine it rolling to feature phones before too much longer.
But it could also be a very big deal because its free texting to your Friends based on just knowing their name and not bothering with their number.