I didn't know there was such a thing as a book trailer until last years NaNoWriMo. When I am on youtube I am not looking for anything book related (exception some of the stuff up about Discworld). But there are people that love them, and authors that swear by them.
I don't know. It wouldn't take much for me to throw one together, for my upcoming book, but do they really get people to read your story?
I would have everything in place. The artwork, and voice overs from the actors on my podcast. The music from the pod cast as well....
Oh hell why not!?