The link to the form to opt-out is here: Yellow Pages Opt-Out, and it seemed easy enough to fill in. I guess we'll see if opting out actually worked next time delivery season comes around (sadly it just passed for me).
I suspect this will turn out to be one of those things, like signing the B.C. online organ donor registry, that I keep trying to do again, only to remember that I already did it once.
On the topic of the yellow pages, I never understood why local chambers of commerce never coordinated local businesses to put out their own yellow pages (digital version these days), and cut out the middleman that was extorting them via a natural monopoly.