Google launched today an interesting feature. It is called Google Sidewiki and allows anyone to comment anything about a site. In short when you browse the internet you can post comments about a site and when someone else who has Sidewiki installed goes to that page he can see your comments, annotations about that site. It may happen that you researched hard to find a site on some subject, so you could write in Google Sidewiki that this is the most comprehensive page about the subject you’ve ever found, this way others will not waste their time searching further.
Google Sidewiki comes in the form of an extension to the Google Toolbar, so users of the Google Toolbar for Firefox and Internet Explorer can use it. Others will have to wait for the implementation of this feature in Chrome or other browsers. To start using it you must install or update Google Toolbar from here
Its an interesting experiment from my point of view, just that every system has its weaknesses and this one’s weakness is the possibility to be abused by all kinds of “SEO experts”.