Came across this site talking about the convergence of blogging and PR. The short version seems to be that people are paying less and less attention to traditional advertising, and the PR industry is looking for a way to get its messages out to people. Blogging comes up as the tool for forming a "grass roots" marketing strategy.
Of course, another way to put it is that if you build a good product, people will like it and tell their friends about it. Some of them might use a blog. But there's really nothing new here, other than people throw away everything coming in the mail slot that isn't a bill, and use Tivo to skip past their commercials.
I can't say I'm sad to see mainstream advertising in a crisis. Even the superbowl commercials have been dissapointing recently.