From the Balance Bar site: The "Balance Bar" is a simple browser extension programmed to allow any user to editorialize any web page anywhere on the Internet. The "Balance Bar" will literally insert your comments/article/rant directly onto whatever web page you would like to expound on. The "Balance Bar" was developed because of the increasing need to "balance" the one-sided and isolated worldview that much of our media sources produce.
I can't decide if this is real or fake. I could see that it would be possible to program a browser to float comments on top of a page. However, the comments would only be visible to you (the browser user). I can't imagine it would be possible for a browser extension to insert comments onto a page so that the comments would be visible to other people (i.e. to actually alter a page that's stored on someone else's server). In which case, I don't quite understand the purpose of the extension. Since I use a Mac, I can't download the program to test what it actually does.