Just a couple of closing thoughts on this subject:
1. News and Information blogs sites are becoming more professional every day. I like to direct people to Silicon Valley Watcher as an example of a professional news blog, but Arianna Huffington's The Huffington Post may be even a better example. Started on May 9th the site includes blog posts from Walter Cronkite. Ellen Degeneres and other well known folks. If you haven't seen it, take a look.
2. I've been talking to a wide variety of "for profit" bloggers over the last couple of months and it is clear that effective business models are emerging. While most discussions of blogging economics are focused on advertising, I've found that ecommerce revenue generated by affiliate programs is the leading source of revenue for most of the financially successful bloggers.
These ecommerce driven sites blend entertainment or information with mulitple opportunites for their audience to click through and buy something (see Manolo the Shoe Blog). I suspect that most visitors don't realize the blog is getting a cut when they click through and buy something, and they probably don't see the blog as a commerce site.
3. The costs of operating a blog are very low and many bloggers report that outside of their time, they only spend several hundred dollars a month on their blogs. Low operating costs combined with the distribution reach of the Internet make blogging an easy business to set up.
4. Based on my discussions with bloggers, you don't have to attract a lot of traffic to have a financially successful blog if you have a strong ecommerce revenue stream. Ecommerce-based bloggers getting as little as 1500 - 2000 visitors per day are happy with the financial returns of their blogs. These folks are not getting rich at this traffic level, but they are running a nice little business that has very low operating costs. If they can scale their traffic to over 10,000 visitors per day the numbers start to get very attractive, and ecommerce revenue can become very substantial.
5. Given the economics involved, I believe we will continue to see the rapid growth of for profit blogs. I also think we will see blogs take on many different forms and styles as bloggers experiment with and exploit profitable niches. Silicon Valley Watcher and The Huffington Post look more like online news magazines than blogs, and Manolo the Shoe Blog looks more like an entertainment site than a traditional blog.