physics - 10:00 pm on Feb 27, 2011 (gmt 0)
Legal and moral issues aside here is the argument that having your book pirated could actually help you.
Someone might download that cache of 2,500 books. They read your book. They weren't planning on buying your book and had never heard of it. They end up really liking your book so they tweet it, facebook it, tell their friends. All of a sudden you've made hundreds of dollars off of this pirater.
In another case maybe a struggling college student has heard about your book and is thinking about buying it. But she can't afford the cover price so seeks it out and pirates it online. She loves it and again tells her friends. You profit when her mom, who doesn't know how to pirate things and has extra money, buys the book. You also profit when this girl gets older, gets a job, and buys one of your future books at the airport.
Emotions and laws aside, that's the argument many who see pirating as tolerable - and possibly even profitable - put forward. There are many more similar examples you can come up with.