NEW YORK -- Magazines aren't just for reading any more. They are the centrepiece of brand identities, core products that can be extended into every avenue of life. Maxim recently loaned its name to a line of hair-colour products aimed at the randy twentysomething men comprising its primary demographic. Last June, Seventeen magazine opened a salon and spa in a Dallas mall, where overstressed teenaged gals could relax with a massage and pedicure on their daddy's credit card. The challenge for brand extension is perhaps a little more acute for the publisher of The New Yorker, an institution that remains...