It looks as Blog*spot users will soon be able to insert a ratings system in their Blogger blogs which will allow readers to rate an individual post from one star to five.
Unfortunately it seems as if they launched the feature prematurely, and the Google team has currently disabled the feature–at least for now.
(Blogger Status) Some users may be seeing star ratings on their posts without having opted in to this new feature. This is an experimental feature that was accidentally enabled on some users’ blogs. We’re currently working to remove star ratings on all affected blogs. In the future, you’ll be able to choose to opt-in to this feature; it won’t appear automatically.
Update: The Star Rating feature has been disabled for the moment.
There is no word on whether a user will have to register for a Google account in order to rate, although if so, they will hopefully add OpenID users to the mix (since Blogger is an official provider now).