Google has finally seen the light. The original Blogger didn't use semantic identifiers for posts, they used a number. You could change the subject and the URL didn't break.
Blogger 1.x used the title as the post name. Change the title, you changed the URL and broke any links.
Blogger 2 uses the title as the post name, but it's a one time operation. You can change the title and the URL remains the same. This is a GREAT improvement.
For example, I corrected the title of this post but the URL shows the old title. I'd prefer a meaningless identifier for the URL, but this is an acceptable alternative.