Online is proving to be a lifeline for retailers. Traffic at stores on Black Friday fell by 52.1% compared with last year, according to preliminary data from Sensormatic Solutions. In contrast, online spending on Black Friday surged 21.6% to hit a new record, according to data from Adobe Analytics. Overall, for the six key weeks of the holiday season this year, traffic in retail stores is expected to be down 22-25% year-over-year. But observers said the declines may be due, in part, to social...