Microsoft Facebook and YouTube apps for Windows Phone 8 show up in Marketplace

Official Microsoft-published apps for Facebook and YouTube have popped up  Marketplace.  The Facebook app is version 4.0, while the YouTube stub is version 2.0.

The apps are designed for Windows Phone 8, and will not show up if you are signed in with a Windows Phone 7.5 handset.

As of yet it is not clear what is different, but we have already seen the Facebook app supporting Fast Resume from the start screen, which is certainly a Windows Phone 8-only feature.