This verse is not a one-liner, meant to stand alone like a pithy maxim, but rather it is one expression in a teaching about light and dark as a metaphor for good and evil:
Ephesians 5:6-20 New American Bible (Revised Edition)
Let no one deceive you with empty arguments, for because of these things the wrath of God is coming upon the disobedient. So do not be associated with them. For you were once darkness, but now you are light in the Lord. Live as children of light, for light produces every kind of goodness and righteousness and truth. Try to learn what is pleasing to the Lord. Take no part in the fruitless works of darkness; rather expose them, for it is shameful even to mention the things done by them in secret; but everything exposed by the light becomes visible, for everything that becomes visible is light. Therefore, it says:
[INDENT]“Awake, O sleeper,
and arise from the dead,
and Christ will give you light.”
Watch carefully then how you live, not as foolish persons but as wise, making the most of the opportunity, because the days are evil. Therefore, do not continue in ignorance, but try to understand what is the will of the Lord. And do not get drunk on wine, in which lies debauchery, but be filled with the Spirit, addressing one another [in] psalms and hymns and spiritual songs, singing and playing to the Lord in your hearts, giving thanks always and for everything in the name of our Lord Jesus Christ to God the Father.[/INDENT]
My interpretation of verse 11 would therefore be that we should not allow ourselves to be deceived by darkness (ignorance, listening to lies, intoxication, refusing to examine what is right or wrong), but rather expose our own desires, choices, and actions to the light (truth, conscience, obedience to God’s commandments, love of God and neighbor).
In the context, I do not think it means to expose the fault of another, but rather to expose our own fault to careful self-examination…
… though upon reading John Martin’s post above, I think this process of self-scrutiny can be extended to the community of Christians, that is, the Church. It then becomes a culture which strengthens the faith of individual believers and encourages them to live virtuously.