This is related to your post from the person who wants to self-pub/post his short stories as a way of gaining presence and followers. My question for you is, could this be done in a comparable way with excerpts from a novel that hasn’t been published yet? How much could be posted as a teaser without the book being considered published and, therefore, tainted goods for any self-respecting shark or agent?
First, let's remember there's a standard for how to judge if a book has been published. Does it have an ISBN? Was it available for sale?
Excerpts from the novel do not have an ISBN.
Generally they're not sold; they're content in a magazine perhaps, or posted on a website, and that's a distinction that's important. The book isn't sold; excerpts were.
Excerpts before publication are covered under "first serial rights" in a publishing contract. If you've published excerpts from your novel, and your agent sells your book, make SURE you tell her since publishers routinely scoop up first serial rights, and you don't want them to do that in this case.
Pieces of novels are often published in literary magazines before a book is sold.
There's no problem with doing this.