I would like to discuss the possibility of adopting BEM for Drupal 8 CSS class naming. BEM means 'block, element, modifier' and is a syntax for CSS class naming that plays very nicely with Object Oriented / Modular CSS concepts.
Please read http://csswizardry.com/2013/01/mindbemding-getting-your-head-round-bem-s... for further information.
Currently, the syntax proposed by BEM is not even possible in D7/D8 because of the way drupal_html_class() and drupal_clean_css_identifier() work together (they turn underscores into hyphens).
I see great potential in this concept for making theming in Drupal much more enjoyable.