Small groups and Bible studies in Western churches tend to offer easy entry and exit points.Limited-run Bible studies (think Beth Moore studies), or 8-to-12 week study groups around a particular topic. These kinds of things are good for what they do--but what is the long term effect? If I don't like the people in this group, it's easy for me to leave them in a few weeks. Within a few on/off cycles, I find the people who are most like me, who I click with, and then I just stick with them. I avoid the messiness of life on life discipleship, and rarely encounter viewpoints different from mine, or things I don't like. The other challenge: limited-run Bible studies are less conducive to movements, because they have extinction built into their DNA. If we want movements that scale to the whole of an area, we may have to make our groups easy to enter but harder to leave.