Sony has stated that they will be end support for the Youtube app on PS Vita. They will also be removing the Maps app and "Near" in an upcoming firmware update.
The update is scheduled for release in March, however Youtube support will be ending today, with the app being removed from the store, and all official support ending on April 20th.
Reddit users are very upset about the removal of the Youtube app, in spite of Sony stating that most of the same features can be accessed through the handheld's browser.
It is currently unknown why these features will no longer be supported, but Sony have posted FAQ's for both the Youtube app and the Maps app.