I'm a pirate! I pirated Skyrim. Why? I bought it on PS3, then realized that it's way better on PC, but I didn't want to pay twice for the same game. =(
I pirated Sins of a Solar Empire. Glad I did, too, because I hated it and deleted it.
I didn't pirate Pirates of Black Cove. I wish I did. I hate that game. Worst money I ever spent on a game.
I pirated Kingdoms of Amalur. Loved it, so I bought it.
I semi pirated Mass Effect. I bought the game, beat it, uninstalled it. Years later, Mass Effect 2 came out. But I had deleted my save game from ME1! So I scoured the web for saved games that matched mine, but could only find the ones that had DLC that I never had. So I basically pirated the old DLC in order to get the save files to work on my computer...
I won't try to justify pirating. I know it saves me money, and I am a firm believer now in demos. As kingnoobe said, pirating helps the consumer save from getting burned in the absence of a demo of a game. I used to love the old Shareware days, like Rise of the Triad. I had the Shareware version, loved it, bought the full version. Why can't we go back to that model? Here's a trial, see if you like it, then buy it. I would support that one hundred percent, instead of feeling guilty pirating a game first.