'Tis the season?

Yesterday Jess was shopping at the Mall of America and witness 3 total meltdowns.  Three separate women yelling at sales associates at stores.  This behavior is something that sadly, happens more often during the holiday season.  So what gives at this time of year?  We don’t understand letting someone working at a store have when chances are they have no control over whatever is making you mad.  So, people who have worked retail (as George and Jess both have) any customer horror stories?