While there is no doubt that the Internet is changing the way coroporations communicate with the customers, it is of far more interest to me how public relations professionals should react. With that in mind, be sure to read the 10 Commandments for The Era of Participatory Public Relations posted by Steve Rubel.
What strikes me as particularly interesting about his set of commandments is that all should be applied whether online or off. What the Internet has done (especially the blogosphere) is make it more urgent for corporations to adopt standards of communication that they should have done years ago. Ten years ago if a corporation violated one of Rubel's 10 Commandments, the worst that could happen is a letter from a disgruntled customer who might also tell four or five of their friends. Today, that customer can reach thousands of people with a blog post that required less of their time and money (postage).
The connectivity of the Internet reduces the margin for error. My advice? Read Rubel's Rules and follow them. Today.