Building groups that work
In tribes of 100-150 everyone knows everyone. We have adaptations designed to allow us to form larger groups and identify group members in other ways: We are the group that dresses like this, wears our hair like that, can pronounce "th", believe X [where X is complex and something that no reasonable person could believe], understand arcane aspects of our native language/dialect, hold particular facial expressions, follow mysterious cultural behavior... So the trick is to be in the correct self-identifying group: the one where members will actually help each other, and be able to do so. And if you're in an attempt to build such groups (like Transition Towns) then I'd recommend working on all those human ways of making a group self-identifying. Of course this will make other people/groups hate you, so you need to keep a lot of it secret. Oops, this is starting to sound like a nightmare. No wonder we want growth to keep going, even though we haven't really enjoyed it and we know it's an environmental disaster.
[This was a comment in response to people trying to set up groups to prepare for Peak Oil]