If a book carries a warning label which states that I’m putting myself at risk of patent litigation by implementing the ideas in the book, I’ve got a problem with that. A big enough problem that I'm not going to reading it.
Pat Eyler on a new book from IBM which states:
If you want to take our methods and create your own software solution to sell as a product, while we applaud your initiative and enthusiasm, you really should first discuss this with suitable representatives from IBM business development. IBM has sole ownership of all the intellectual property described in this book, all of which is protected by U.S. patents, both granted and pending.
From time to time I'll contact authors to see if I can use the code in their books; both "Practical Ruby Projects" and "The Ruby Way" contain code that has ended up in Ruby music-generation experiements I've done. I think failing to include a license for the code in your book is a very common but very rude faux pas on the part of tech publishers today. But actively prohibiting people from using the code or even the ideas in your book is pretty damn strange. Certainly, if your target market is people who want technical ideas which they can't use explained in great detail, you're not planning to sell a whole lot of books.