After 4.5 years of service, the PageSpeed Service team regretfully decided that the time had come to re-focus their efforts elsewhere and on 5th May announced that PageSpeed Service will be turned down. If you are using PageSpeed Service, you must change your DNS before 3rd August 2015 or your site(s) will become completely unavailable on that date.
Official Link: https://developers.google.com/speed/pagespeed/service/Deprecation
This will affect a LOT of people....