I haven't done this with RPG material, but I have done it with music. Just recently, after spending months in futile search for a boxed set of CDs that has been OOP for at least half a decade, I Googled up a listing for it on a torrent site. Two hours later, I had the music on my hard drive and was happily listening to it.
The way I figured it, neither the artist nor the publisher would have benefited from the sale had I been able to locate an after-market copy. Furthermore, the dissemination of a lower-quality recording with no attractive packaging will, at worst, spark the interest of people who never would have heard the music in the first place, and, at best, perhaps inspire a re-issue of the original, high-quality production.
To be clear, if the product had still been in print, or even readily available but used, I wouldn't have bought an unauthorised duplicate. And, to be to the point, my attitude toward OOP RPG material is essentially the same.
!i!