I recently had a conversation with a friend in which I told him that everything written on Facebook can be seen by the Facebook admin staff. As a software engineer and database administrator I know that if one user's data can be displayed to another user on a website, then that data can likewise be displayed to other admin staff. Of course this excludes data that is stored but never displayed - such as hashed passwords. Anyway, as far as I know, Facebook currently uses MySQL to hold their indexes and Apache Cassandra to hold the data for these indexes.
Can someone point me to an article that either shows that Facebook admins can read user's data at will, or that admins of this particular combination of database software can read all data stored within. I would like to be able to demonstrate this to someone who is unfamiliar with databases.
p.s. I realize that Facebook is huge and therefore the chances of any admin having the inclination to read my data are low, nevertheless, this question is about possibility, not probability.