Fresh install of Wordpress 3.8.1 and _s and for some reason jQuey doesn't load.
If I switch themes to _s 1.2 release it works fine.
Here is my test site http://richardsmith.co.za/genwest/
jQuery isn't loaded out of the box because none of the scripts that are used in a bare _s install have jQuery as a dependency. The 1.2 version dates back to the before the current navigation.js replaced the old small-menu.js (which did require jQ).
@sabreuse Thanks so much. Makes perfect sense.