I would like to point out that software piracy is different from copying music, books, or movies.
Many people use the "I wouldn't have bought the application anyway" argument for justifying software piracy, and Mr O'Reilly points out that if anything, piracy may be even good for your sales since it gives you free advertizing.
My point is that piracy indeed doesn't bother the author of the pirated program much. Instead, it's a problem for competitors, since competing on price is no longer possible.
Suppose I make an image editing application which focuses on simple web grapics, doesn't offer all the bells and whistles of Photoshop, but for $19.95.
People who already have a pirated version of Photoshop will also not buy my image editing application, even though they probably would have in a world without piracy.
Books, movies, and music rarely competes in price/performance ratio, so this is a different matter.