I upgraded to 8.1 a few weeks ago and just realize the other day that I'm no longer getting facebook messages in my message hub. Researching a little further I discovered I needed to download a separate app (Messenger), and I'm now getting notifications similar to how it worked on IOS -- except Windows implementation of it is terrible (IMHO).
What happened to Facebook Hub integration? That was probably one of the main features that I loved about about the OS and separating it feels like a major step down. Not to mention that Messenger appears to drain my battery like no tomorrow.