An amazing new Google tool is going to have huge implications for the advertising and public relations industries.

Google Sidewiki is a browser sidebar that lets you contribute and read information alongside any Web page.

User-added comments–whether supportive, critical or raising a question–appear as a sidebar on the page. You also can share Sidewiki entries through Blogger, Facebook, Twitter and Google profiles.

You can even add information that criticizes a competing company on its own Web site–and vice versa.

Google Sidewiki is sure to make some big changes in the way Ad and PR professionals use the Internet, because companies and individuals on the Web can no longer hide or refuse to post critical comments. Now, they have to deal publicly with comments, whether they are good or bad.

While much positive and helpful information can be disseminated this way, there’s also great potential for abuse and misinformation.

Ad Agencies need to carefully monitor their clients’ Web sites, as well as their own, for Sidewiki entries and be ready to respond promptly to criticism, misinformation and questions.

Don Beehler provides public relations consulting services to small- and medium-sized advertising agencies and businesses.