According to Neil Gaiman the answer is a resounding "No!"
I was going to post this link a while ago and then reconsidered because I know that many published authors, some of whom I know personally, are deeply offended by the piracy of their work. I can understand this and feel for them but I think the point that Neil Gaiman is addressing isn't about the ethics of piracy as much as it is about the impact of piracy on an author's book sales.
I decided to publish this link after reading a blog by Timo Boezeman entitled, Fighting Piracy is the dumbest thing you can do. He made what I thought were interesting points about the financial impact of piracy.