Intelliseek and Edelman have released a study on the impact of blogs. Their document "How Real People Are Finally Being Heard," gives a nice synopsis of this new web phenomenon, including a very solid definition of blogging and a brief rundown of its early history:

This new and growing critical mass is forcing marketing professionals and company stakeholders to think differently about how they go to market. Bloggers are speaking and being heard in real time, and only recently has the marketing community begun to grasp bloggers’ impact on brands, business and issues. Because of their speed, bloggers can and do alter the volume and tone of any conversation. Gone are the days of waiting months to get reliable feedback on an initiative. The new reality is this: any blog author with a passion for what you’re selling knows what you’re doing the minute you do it—and maybe even before. Bloggers comment immediately, and marketing and business professionals can quickly lose control of the conversation.

Very well said, and although they did not mention it directly, I believe they understand that blogs are a neutral force. They definitely can provide the negative impact per the examples cited in the paper, but they also present a tremendous upside. The scope of the 'Media Relations' department has not only increased, it has also become more interesting.

The white paper can be downloaded here (registration required).