A quick example. A friends company found a popular blogger who had spoken highly of the company's brand. Just prior to launching a new product, the company sent the blogger a free sample, inviting him to review it with "no strings attached."
The end result: The blogger wrote a favorable review and generated a flood of comments. So the company got nearly free publicity and feedback. This blogger is a very popular blogger on a very popular blog with thousands of followers as well as content that is syndicated. Product sales surged 35% right after the article/review was written. The traffic to the company's website from the blog tripled (as tracked by google analytics data). Welcome to Marketing Web 2.0.