To make the plugin user friendly it should support normal activation.
On activation, should test if it can write to wp-content folder and if memcached extension is available (test any of memcached functions/classes exist).
Ideally, if it can write, it should ask the user to accept the caching php script to be copied to the correct location.
A hook for uninstall/delete could be to also delete the cache script (testing if could do it for alerting the user if not).
With the idea of the user to do manual steps, makes the plugin available only for developers and more technical people.
