Do you want to allow anonymous users to comment, but also want to ensure that the email addresses they enter are THEIRS? Not So Fast creates a new column in the comment approval queue labeled "Email is verified?". When anonymous users post comments, an email is sent to the address they specify. The email contains a link which, when clicked, will register their address as being verified. Site administrators can then determine whether to approve or delete comments based on this new criterion.
Not So Fast works as an excellent spam deterrent, but also permits site administrators to keep in touch with (and keep records of) the anonymous users who post on their sites.
I am open to suggestions about future directions for this module.