UPDATE: 2014.1 - Client file caching will now be enabled for 2014.1 sites

Client file caching will now be enabled for 2014.1 sites. This should significantly increase PageSpeed http://developers.google.com/speed/pagespeed/insights/; and other similar scores.

Read here for more info:
https://developers.google.com/speed/docs/insights/LeverageBrowserCaching