it is axiomatic for the follower of the christ to be in the world, but not of the world.
that said, the obvious follow-up is how. how can we walk that steep crevice without falling into the world -- so earthly minded we're of no heavenly good, or into religion -- so heavenly minded we're of no earthly good.
it seems clear that the danger of us being to close to the lord, so we are of no use to the gospel is quite a stretch.
what can be said, however, is that we can be so tied to the church, and by that i mean christendom's expression of it, that we cannot be seen by the world as followers of the christ, only a follower of church. and this may be the most devastating criticism of the believer.
this comes across, most of the time, as being oblivious to the needs of the world. it's not that we don't care, but we care mostly because our churches are shrinking (the incredible shrinking church). but throughout this we miss the need because we are locked into our own categories of life and our understanding of what people should be like.
said another way, those not like us are forced to conform not to the jesus-way, but to the church-way.