Counting the cost

"If you lead a group that allows anyone to join, for free, your group might be large, but it's not tight, it's not organized to make important change. Commitment slows things down in the short run, but ultimately aligns interests.", Seth Godin

Exactly what I've been thinking! In church, we cannot count on everyone who comes our way to have the same level of commitment to the mission and to the group, especially if we are a faith family who is attracting people from outside our group. So, how do we get new people to "buy-in"? By keeping the barriers low, we can pad our numbers, but isn't our mission larger than that?

I'm looking for answers here, or at least decent ideas full of compassion. The world is watching!