Proskauer Rose’s New Media and Technology Blog gives some solid Sidewiki advice here.

Let’s say that anybody could write comments on your Web site that were visible to third parties and that you couldn’t prevent it. Those comments might include links to competitive Web sites or products, defamatory statements, or just unwelcome negative comments. And let’s say that your only recourse, if you felt the comments were inappropriate, would be to e-mail a complaint to an enormous media company that might or might not agree that the comments should be removed.

Well, if you download and install the Google Toolbar, and navigate to your Web site, you can find out if that is happening on your site right now.