From the Editor's Introduction to Dietrich Bonhoeffer Works, Volume 1: Sanctorum Communio:
When Bonhoeffer says, "the church [Kirche] is Christ existing as Gemeinde," this does not mean that an institution calling itself church defines where Christ is communally present. On the contrary, it is not a church organization that defines Christ, but Christ who defines the church. In other words, it is precisely where, and only where, 'Christ-exists-as-Gemeinde' that we find the 'church' (Kirche).
Now that's an interesting test for ecclesiality.