It's kind of funny to see people talking about this, and I wonder how many are actually serious authors or publishers. I'm both. My books have sold over 500,000 copies in print. And yes, they have been pirated in ebook formats, and if I search I'll find them via the usual suspect repositories.
The issue isn't whether stealing stuff is right or wrong. It's about whether there is any point in trying to stamp out piracy if you are an author or publisher, and I can tell you that the answer is that it's simply not worth it. If one sells millions, one can hire someone to do that kind of work, but for most publishers/writers, you could spend all your time tracking down and doing DMCA's and it's like swatting flies.
Writers write. I'm not a lawman. If I'm tracking down rapscallion scofflaws, I ain't writing.
So, if I could wave a wand and make all the theft go away, I would. But as a real life working writer/publisher, I have the next book and the next book to do.
Here's the reality for writers and publishers. If you can't stomach being ripped off, do something else, or make sure you don't do ebooks (although now people are scanning in physical books)
Even for the major publishing companies, including the multinationals that have published most of my books, THEY don't bother either.
Does piracy affect me income-wise? Maybe some. Probably more so since I've become a publisher and venturing into the industry on a different scale and basis. For the most part, I agree with Incredibill. Professionals who are my market will buy if they see value. They aren't all that likely to steal. And those that steal, probably wouldn't buy anyway.