An interesting read on the rise of ad hoc bands of armed citizens - some from the U.S. - who got fed up with the local drug cartel and took up arms in their own defense.
Mexico has been in a state of quasi-failure for a long while now, with drug cartels owning whole towns and regions. Criminal feudalism that, in many ways, is a crap-hits-the-fan situation of its own.
As I see it, while most folks are most worried about random mobs and roving gangs in a collapse scenario, the bigger threat will come from corrupt groups trying to assert themselves as the 'new' government or regional power...exactly what the cartels have done here.
These aren't going to be groups that randomly come together, but existing organizations with manpower and resources pre-collapse. Likely, organized criminal gangs will make a play for power, as will extremist groups...but also, government and political organizations would make plays to retain or expand their power, too.
A band of four or five poorly equipped thugs a survivalist family or two can fend of. A large, well-equipped criminal organization or despotic officials with corrupt, militarized law enforcement on a leash...less likely.
Resistance to these levels of threat to safety and freedom would require numbers, some level of training and logistic support.
Further complicating matters, the 'good guys' would likely be starting far behind the curve and at a disadvantage to whatever organization was trying to assert itself as the new boss in town.
Anyways, a few thoughts for ya'll. Worth thinking about.