My justification for pirating music is simple. Most of it is simply too expensive for me to purchase. As a fan of music from countries such as Japan, Korea and others, I often find that importing a CD is a pointlessly expensive endeavor. Digital downloads are fine, I often pay for those, but physical media tends to be around the ã20-30 mark, and then almost double that for the import tax and delivery, bringing an hour-long CD up to the cost of a newly-released videogame or a week of grocery shopping. I refuse to pay that amount, but I still want to enjoy the music. Hence, piracy.
It's also key for games. There are many games I've pirated to test if they will work on my system. I'm not paying hard-earned cash just to find out I don't have the right chipset, or my clock speed is slightly off, or my OS is the wrong bit type and is not supported (All of this is information you don't find when purchasing the games, you merely find the minimum and the recommended specifications. Anything in between, your guess is as good as any.)
Honestly, the industry can complain all they want about how piracy kills the market. Maybe if they put some more thought into what they're putting out instead of the countless carbon-copy Disney princess singers, the pseudo-pop/rap wiggers, the boybands who can't play instruments and struggle to sing without autotune, maybe once they stop all that more truly talented musicians will be able to shine and earn the industry a lot more money.
Also, there are plenty of artists I'd have never purchased albums and merchandise from if I hadn't pirated their work originally. I consider that a fair trade.