The same arguments apply for ebooks as for music:
1) Once the intellectual property is in usable digital form, it WILL be pirated if it has any value at all.
2) The cost of trying to stop piracy is high. Even the RIAA has had very limited success despite huge expenditures.
3) For years, artists have been encouraged to not make music sales their only source of income, and to focus on live performance revenues, branded collateral products, etc. The same is true for authors of business books: if you've been ripped off a million times, you certainly have viable speaking, consulting, and product sales opportunities.
Note that I'm not saying piracy is OK or that it should be tolerated. Rather, my point is that if your business model is based on someone stopping piracy of digital IP, you have a problem.
I think IncrediBill and those disagreeing with him really aren't that far apart. It's true that the odds that someone who downloaded a compilation of 2500 books, or who figured out how to download your book, would have shelled out the cash to buy it are very low. At the same time, one can't argue that the revenue lost is zero; at least a few legitimate buys are lost to illicit downloads. The only question is the magnitude - are we talking 2%, 20%, or 80%? For business books, I'm guessing at the low end of the spectrum. Undoubtedly it's higher for entertaiment media like music and movies.