Ok, you can start using your Vita again: the Facebook app is back and ready for download. Before today, new buyers who went straight to the PlayStation Store in order to tell their friends about the new member to their PlayStation family would have been left disappointed and may have even had to move to their computer, laptop, smart phone or 3DS.
The official PlayStation Twitter account informs us that the Facebook app is ready for business and fully functional. That's not to say that there was anything much wrong with the app to begin with, rather that the problem was on the Facebook side of things. I haven't had much chance to play with it yet, but it seems to be OK and I've so far learnt that most of my friends and family should probably find a hobby or, failing that, do something more interesting to share with me.