I figure that if the author is afraid to toot their own horn then who will do it for them? And if an author writes a book about writing it's almost certain that they will include clips from their own writing when showing a technique. That isn't part of the normal book promotion either. It does solve the problem of copyright though. I mean you have to prove fair use if you use clips of someone else's writings in your book on writing, but if you use clips from your own that isn't an issue. At least as long as both books are published by the same publisher anyway.
