Along with issuing tickets to those lining up, many Best Buy stores conduct full-scale dress rehearsals with some employees working inside and others lining up as customers to help managers predict traffic flow and make adjustments before Black Friday.

Two incidents last month underscored the problems that can occur.

Orlando Magic NBA player Dwight Howard prompted a huge rush on a Florida GameStop store that overwhelmed employees when he started a scavenger hunt on Twitter promoting a basketball video game giveaway.

About a week later, a woman who claimed she won $1.5 million in the lottery offered to buy clothes for customers at a Burlington Coat Factory store in Ohio. When she backed out, and it became clear it was a hoax, a riot ensued.