I can't resist introducing you to Super Librarian, just in case you haven't already met her. Its a 35 second promo video from McCracken County Public Library, Kentucky. This brings me to an interesting point.
We can sometimes be guilty of mistaking promotion for pedagogy when considering YouTube materials. Most of the library ones that I've seen have been more about promotion and orientation, rather than teaching or facilitating student learning. Maybe there are some new offerings out there being created with superb pedagogical credentials? Anyway Super Librarian isnt one of them!