For luxury fashion brands that pride themselves on elitism and inaccessibility, this may be the most difficult challenge in developing a social media strategy.

Five years ago, when Phoebe Philo was named the creative director of the luxury fashion house Céline, Ms. Foley was miffed that she had been among the last to learn of the appointment.

Destroying old stock is a practice not just of luxury brands but of less prestigious fashion brands.