Libraries are creating several styles of YouTube videos.
Some are practical tutorials, such as the University of Texas libraries' video on how to find a book. I can see this being used as part of bibliographic instruction in classrooms.
Others use the videos to convey a single message such as Texas Tech's video with no voiceover, just techno music and video of students using a variety of computer programs, such as 3-D animation, and, oh yes, one shot of a student using a book. Message: We are techno savvy and we have the tools to prove it!
The University of North Texas Portal to Texas history uses a video to raise awareness of its existence as well as showcase some of the intellectual content of its collection using rapid fire images of some of its holdings. It's very entertaining as well as informative. Watch it by clicking on the Thing 20: YouTube title of this post.
Other libraries illustrate their library activities, as is done by the Round Rock Public Library, which uses orginal music in English and Spanish to highlight its Texas Reading Club.
Most library videos have been created in the last two years. They don't tend to have a lot of hits, but that may not be a measure of success. Most are aimed at a limited audience, such as a student population or a city population. Now if we could only get a library video to go truly viral. Hmmm...