While YouTube app works for playing videos, I haven't been able to make use of the various "share" options. I click on message, email etc. and nothing happens.
Well spotted - same for me on a 4S.
. . . Skype for me crashes when tapping on Messages as well.
Edit: iPhone 5
I don't use Skype for messaging, but a couple of people have mentioned problems with this now.
I'll update both YouTube and Skype on my first post list.