Ads invading blogs

Interesting article from Chicago Tribune's Mike Hughlett about commercials invading the blogosphere. Mentions initiatives from Starcom MediaVest Group (Publicis) , TracyLocke (Omnicom), as well as Google's AdSense program.

Again raises the question - does blogging as a channel become more or less powerful once big business advertising dollars fly through it? Does it become more or less an opportunity for PR folk?

And/or do mechanisms like AdSense make it more likely that it will become as crowded a channel as email?