I think it's the Catholic schoolgirl plaid skirt and white shirt combo that makes tartan plaid such a perennially hot fashion. Girls like the naughtiness of the fashions and guys like the naughtiness of the fantasy.
Tartan is everywhere from the catwalks to the dogwalks (dog collar) to the man walks (guys' shoes and ties) and even to the guys' favorite hangouts (the twin recliner).
Implications - With the recession came a "back-to-basics" approach to fashion for money-crunched consumers. Consumers are now embracing styles and patterns which were previously deemed unattractive. Companies can produce goods that reflect this return to basic patterns to appeal to a large group of consumers.