Milgram's most interesting insights are his attempts to explain why people don't intervene. Are people just too scared? Not necessarily:
Group formation is difficult when
people are stood one behind the other, all facing in the same
direction. Consequently social order is weak.
Milgram thought queue-jumping is
tolerated as long as it doesn't threaten the line too much. People want
to avoid social disorder because their own interests (getting served)
are tied up in an orderly queue.