A few people have brought up the point that, if they choose to go the traditional route to publishing, having their entire book published on their blog may very well work against them in getting a book contract.
There are some optional ways of following this challenge, in those instances.
1. Write your one chapter every day, but only post on your blog about the writing, such as how much you wrote, what part of the story you were working on, what was easy about it, what was difficult about it, whether it stayed on plan or strayed from the original plot idea, etc.
2. Write your one chapter every day, but only post a small (one paragraph) excerpt from that day's writing as your blog post for the day.
3. Blog your book as per the original plan, but leave out important chapters, which will only be seen in the finished product. (This is a good idea even for those who plan on self-publishing.)
4. Don't blog your book at all, but use this challenge as the impetus to write a chapter a day anyway.
5. Blog about subjects related to your book or about topics your readers will enjoy reading about. (This is a great marketing technique.)
6. Do a 30 day promotional blogging adventure, with prizes and give-aways. Have your readers answer questions to previous books you've written in order to win prizes. Let them give you input on where they see you next book going or who their favorite characters are in your stories. There are many ways to make this month-long writing challenge a great marketing strategy for your book before it even becomes available.
I'm sure there are other ways to go about this and still be part of the Blog Your Book in 30 Days challenge, but these are a few ideas for you to consider.
Don't forget to follow the Blog Your Book in 30 Days Facebook page. (If enough people join the challenge, we'll create a Facebook group for discussing our books.)