I would say this issue could be resolved the same way maximum occupancy limits are established. Require buildings to establish maximum egress numbers (i.e. how big a crowd can be before a building is not allowed to open at all until the crowd is partitioned down into groups that are below the maximum egress number. This would force a pod-like crowd control solution that is observed the the NYC NYE event.
With a solution like this, Walmart would not have allowed a 2000 person line to form. Instead they would have had to partition the line into something like 20 groups of 100 people. Each group would be physically separate from the other with a buffer.
Cost of managing such a crowd grows proportionately to the size of the crowd you attract and costs are only really incurred if a crowd ever forms.
The only added cost is the work necessary for someone to calculate a maximum egress group size per building entrance. That's probably minimal extra work and likely to be proportional to the figures calculated by the fire department for getting people out safely in the event of a fire.
With a solution like this, Walmart would not have allowed a 2000 person line to form. Instead they would have had to partition the line into something like 20 groups of 100 people. Each group would be physically separate from the other with a buffer.
Cost of managing such a crowd grows proportionately to the size of the crowd you attract and costs are only really incurred if a crowd ever forms.
The only added cost is the work necessary for someone to calculate a maximum egress group size per building entrance. That's probably minimal extra work and likely to be proportional to the figures calculated by the fire department for getting people out safely in the event of a fire.