Installation documentation mentions memcached only under requirements, but for somebody new to MediaWiki and OAuth extension this is unclear. Also, installation without memcached fails in a strange way without clear message. I spent quite some time debugging why it does not work. I think there should be few lines how to run a simple local memcached in installation process for OAuth and then link to the memcached paage for more information. And OAuth should throw some error mentioning that memcached is missing.
(BTW, I am running MediaWiki + OAuth on SQLite and it seems to work.)