That information can be found under Tools > Delete Blog, if you select the option "Free up the blog name so that somebody else can use" it, the following notice comes up: "At this time, there is no way to free up a blog name. Once you've registered a name, it's yours. If you're trying to free it up so that someone else can use it, you might want to try moving a blog to another user instead."

The option is there because the question comes up a lot, and if a user selects that option, they see the answer immediately.

Let me know if you have any more questions about this or have suggestions about how to make that message clearer.

I've been here for over 6 years and I have never heard that "free up the blog name so somebody else can use it" notion espoused here. the only place I have heard it is at Blogger.

In order to delete any blog one must be logged in under the exact username account that registered the blog. Provided you are logged in under the username account that registered the blog you can delete it by using these instructions. http://en.support.wordpress.com/delete-site/