I've never used any warez software, so I can't comment on that, but I've used your method for many movies that I've bought recently. Watch it online, see what it's like, then buy it. The quality of warez movies is usually so bad anyway that if you really want to see what the special effects are like you need to buy it anyway. I've also used warez versions of movies I already own (Star Wars trilogy for example) so I have something to watch on my pc when I'm writing a paper for example.
So anyway, I think warez is a bad idea for software but a tolerable idea for movies/music.
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"It is by the goodness of God that in our country we have those three unspeakably precious things: freedom of speech, freedom of conscience, and the prudence never to practice either of them." - Mark Twain