Today's New York Times has an interesting article on book trailers. Just the other day I posted a blog on these things, a first attempt to provide a rough taxonomy (read that here). And today I had lunch with a writer friend who has a book coming out this fall: trailers, trailers, trailers, that took up about 50% of the conversation.
For shy authors, may I suggest a "TPA" (see category #2). Most authors opt for "Author Stars" (category #4); and in many cases, this is not, alas, an optimal strategy.