It's definitely a trend.
Hugh at gapingvoid (a VERY funny blog) has put his "How to be Creative" book proposal onto his blog. I've been reading Hugh's blog for a while, and I'm often shocked by his ideas --- in a good way.
In a blog item today, he says he has publishing interest already, one short week after he posted the proposal.
There you go: as I've said before, get a blog, get a book contract.
The beauty of blogging a book proposal is that you get to gauge the response within a short time. If there's NO response, you know the idea is a dud, and it's back to brainstorming better ideas. :-) This saves mailing out dozens of query letters, and heavy, expensive packages. Hmmm…