This post is more of a question then an answer. YouTube is one of the most popular sites in the world, and quite a few of the videos get millions of viewers. Reaching millions of people is exactly what writers want to do. But writing is not a visual art form, so how can we use video to market it?
Home Videos: These don't directly relate to your writing career, but these kind of videos can get hugely popular, and getting people to your youtube site will help introduce them to you. People will start knowing who you are. A link to your blog from a popular youtube video could help you get huge blog traffic. An example of an enormously popular home video is David After Dentist.
Comedy Series: These can get a lot of hits too, and when its a series people keep coming back. Write up some funny characters or do something creative to make a video series that people will tell their friends about. Again, this will just help people become familiar with your name and hopefully direct people to your official website or blog. An example of this kind of series is Miranda Sings.
Video Podcast: One way is to make sort of a video blog and just film yourself talking about writing and whats going on in your writing career. This is simple, and may not be as easy to get popular as some other kinds of videos, but the people who will be watching videos like this are kinds of people who are already interested in books, and could potentially become very loyal readers. There are a lot of these out there, so I'll let you find which ones work best for you.
But most of all, what are your ideas about this? YouTube's popularity makes it a marketing tool that any artist cannot afford to miss out on, so how do we writers use it to the fullest advantage?