I see your point, yvanleterrible, and I don't speak against it, but I personally would prefer to move on to something that has a higher percentage of worthwhile content, than to dig through a proverbial pig sty to find only a single small pearl -- it'd have to be a pretty nice pearl to justify the muck.
Besides, I, at least, don't mean that I toss a book if I don't find it absolutely riveting from the first word, it has to be pretty bad for me to give up on it.