Memcached common misuse is to use it as a data store, and not as a cache.
Never use Memcached as the only source of the information you need to run your application. Data should always be available through another source as well.
Memcached is just a key or value store and cannot perform query over the data or iterate over the contents to extract information.
Memcached does not offer any form of security either in encryption or authentication.
