Reactor Digital uses Memcached
As part of the cacheing system within Drupal.
Memcached mainly took care of creating and rebuilding the REST API cache once changes had been made within Drupal.
csmith932 uses Memcached
Distributed cache exposed through Google App Engine APIs; use to stage fresh data (incoming and recently processed) for faster access in data processing pipeline.
The Independent uses Memcached
Memcache caches database results and articles, reducing overall DB load and allowing seamless DB maintenance during quiet periods.
eXon Technologies uses Memcached
Used to cache most used files for our clients. Connected with CloudFlare Railgun Optimizer.