I occasionally pirate, but not a lot.
Let me give some examples, and how I justify them to myself. Now, when I say justify them to myself, I know it is still a violation of US and International copyright law, and I am willing to suffer the consequences if I am ever taken to court.
1) A couple musicians from the 80s, they were not big label, most people never heard of them. One had a video make MTV but they only showed it twice. I had every tape of theirs, and played them until they wore out. One of the artists, her label did not feel it was worth the effort to digitally remaster her early work, and she basically went out of print. I found vinyl rips of her early stuff, and grabbed it. The other, his stuff was digitally remastered but also went out of print. When he wanted to get his band back together for a single concert, he asked his label if they could do a short run of his discography. They refused. He asked for a short run of just his greatest hits. They refused. He offered to finance the pressing himself (he had made money in cinematography since then), they refused. So on stage, he told his fans "My old label won't let us offer you our music anymore, so if you find rips of it on online, have at it, I don't care" - technically and legally, it is still piracy, but that was when I stopped looking for CDs of his work to replace my worn out tapes on eBay and just downloaded it.
2) I am member of a closed invitation only site that torrents television shows. I only use it for shows where I intend to purchase the season when released (IE Stargate, Sons of Anarchy, etc.) or for time shifting. With respect to time shifting, most of the shows I like can already be legally time shifted via my cable company, but their compression is so horrid - especially in dark low contrast scenes. The encoding done by the torrent scene is a hell of a lot better quality, and I can watch it on my PC.
3) I use Linux exclusively, and netflix on demand does not offer a Linux client. For some shows I could watch via netflix with my wii, I just torrent them and watch them on my PC.
I do understand the value of US/INTL copyright law, and I comprehend my self justifications are just that - it's still illegal, but I don't really care, not for the use cases where I do it.