You clearly don't know what you are talking about.
It is possible for anybody to sign up to Google Groups and use their system to flood usenet with libellous nonsense about anyone they dislike on any groups they subscribe to. Google will not remove any content posted to usenet. This is their policy.
So, what happens when trolls and kooks decide to smear you on usenet using Google Groups as the way in? The posts that they make are picked up by many site owners who import them to their forums using any number of scripts. The libel is then spread from usenet to the web and is perpetuated there.
You take a person with an uncommon name (like mine) who you dislike and you start spreading all sorts of vicious lies and untruths about them on usenet using Google groups. People looking at you for things like jobs or contracts search your name using Google and what do they find? Well... use your imagination. Do they believe it? Unfortunately if it's controversial enough for them to be in doubt they would sooner pass you over than take the risk.
This has happened to me personally.
Along comes this Google Notes rubbish and those same kooks and trolls now have the ability to add rubbish information about your websites that you can do NOTHING about except plead with them to remove it. Given their policy on groups I seriously doubt that they will moderate any notes made about websites that are on the net.
If anything I hope that the internet community will use common sense and reject this concept completely.