I don't think you're thinking far enough ahead Tim.
Publishers are in danger in a future where individual people and their skills can be matched to individual people and their needs.
Take a look at the traditional book process. Acquiring Editor gets and author who works with a developmental editor who passes the book to a copy-editor and artist who pass the book to a printer who gives it to a distributor who sells it to the retail store who sells it to a consumer.
That's a lot of people to have to support on the sale of a book. Imagine that there are no publishers, no warehouses, and possibly no printers. There is just a website that links people together and Amazon with a lot of print on demand press thingies.
Here is how that can play out. An author wants to write a book. He knows it has a limited audience, but he wants to do it anyway. He goes to the skills trader website and finds that there are several editors who want to edit books like his. He finds one with the appropriate time, skills, fess, and reputation, and he teams up with him. They produce a book that they need to have copy-edited. The author goes back to the website and hires a freelance copy-editor. Then they apply a template that they purchased from an interiors person and give the finished PDFs to Amazon. Through Amazon, and some good search technology, the author's book can now have the widest distribution possible to its limited audience.
You argue that publishers like O'Reilly have reputations that help to sell books. I argue that Author/Editor comibinations will be new brand names. Movies are already like this, you watch because of the story and the star. Books are also, does any child care who publishes Harry Potter books? Likewise music. I'm not going to stop buying Sting music because he now works with Sony. It's still Sting.
The change will go further than you think. P2P will not only enable niche products to get maximum distribution, it will also enable skill sets to be matched to skill needs without Labels or Publishers getting in the way and taking a cut.