That's a question for those who use themes provided by others and found on Drupal.org but want to add a region somewhere in the theme, most usual place would be above the content, because the CONTENT region which already exists in most themes is indeed after the content, so when you put a block in the CONTENT region it ends up after everything, one node, the tags, the comments, etc.
So what if you want to add a region to a Drupal theme?