In November of last year, Aaron noticed a spike in memcached traffic, which we were eventually able to attribute to Wikibase client fetching the SiteList on every request. When Katie fixed it, outbound memcached traffic nearly halved.
We're now back to the same rate of outbound traffic as then, and the culprit appears to be the same key.
See: http://i.imgur.com/v9ebld6.png
