1. Get more input.
2. He wants the book to grow. Possibly a wiki format in the future.
3. Great propaganda.
I would add to this list in a few ways:
4. Establish authority- hinted at in the three reasons above, this sharing of information helps establish Ian as the authority on internet marketing that he is. While some of our competitors may write articles, they don’t put their books online for free. Ian is saying, here is how I think, now interact with me about it. Godin did a similar thing with the Ideavirus book, with one crucial difference:
5. Search engine food- Godin made his book freely available in PDF, which is not as good for search engines as plain text. Right now, Ian’s book is online as it is written. Over the next months he will be rewriting parts for SEO. His site conversationmarketing.com currently has 250 pages of content. It had 197 before. And those 50 additional pages of content can be very keyword rich.
What this means to you:
Release information, unless that is what you are really selling. Portent is selling internet marketing expertise in seeing the big picture and doing all the parts so they fit together well. We are not selling a book.
You are not selling manuals. Or books. Or CDs. Use those items to get more people to come to buy what you really are selling.