I try to make a new theme, following this : http://devdocs.magento.com/guides/v2.0/frontend-dev-guide/themes/theme-create.html .
After I save registration.php, admin page crushed.
Also, folder /app/design/frontend/Magento is empty. Luma and blank theme files are not there.
Found the same thing as far as the directory structure not matching earlier tutorials ... it appears that the latest available download for Magento 2 (ver 2.0.0 - Added Nov 17, 2015 ) has changed since the tutorials were made. That's the only thing I can think of to explain all the differences...
Been nice if they released accurate help guides with this release considering how much different it is.