The context of the incident probably dictate the efficacy of a group response. Most events in the modern world are essentially over on a tactical level by the time you could hope to organize the average community or group of neighbors.
.................Other thoughts?
My thought is that we are talking about an extended period of duress that more or less unfolds with various challenges and difficulties that is at least regional (multiple state) in exposure.
.............I think that the concept, which is inherently a good one and has obvious benefits, would require a significant amount of pre-planning and efficient execution of that plan with the group goal in mind as soon as an incident was imminent or occurring. Good luck finding a group that is both motivated and dedicated enough to pull than off in 2010!
Other thoughts?
I think that we should define the discussion to city-state or regional or national. City-state size I agree a group getting together would be tough...just because of the logistics...it will likely be some type of event(s) that will cause a quick decision to be made and will be over relatively quickly. I think Katrina was over "relatively quickly". Now there is lasting damage, but everyone very soon got food, water, shelter and medical attention. It would be tough for anyone but neighbors to organize and move as a group. I think, unless blessed with neighbors of like thought, this is unlikely just as you have said.
Longer term regional or national events that it does not make sense to move because there is nowhere to move to are different. They would be large in nature and either sudden (you can't really get away, i.e. nuke war) or they unflold more or less slowly. The more or less slowly is what I have in mind. In the slow unflolding scenario I think people of like thought can come together for mutual benefit. I believe our most likely sceenario today is something large that unfolds slowly...the economic mess we are in is unfoldling slowly...if the bubble bursts it will be sudden, but the lead up is slow and some people are prepared. The caveat to a group is like mind and with me like mind means being prepared and aware which now means having some food and supplies to get to the "other side" of the economic state we may soon see split from this side to some other side.
I don't think it will be to benefit the group...this is a philosophical difference I hope I get right in my explanation. It will be the group benefiting the individuals who think the same, that will be most successful. What I am trying to say is that people with the same ideals, will work and sacrifice the same for those common ideals not the preservation of the group...the group is preserved but because they all share in the same mindset...we lay our life down for our child...or a child in the group...because that life is precious...we help those who are sick and give them our share of the food because we believe that is what is right. We don't extend ourselves to those who chose to stick their heads in the ground because that lessens our chances of getting to "the other side" whatevere that is unless they can provide long term benefit and now are like thinking. I hope I am making sense here and, Rob, this may be what you meant.