...The mere fact that moving a talk-show host from 11:30 to 10p.m.—a banal decision, on the face of it—has occasioned so much breathless coverage is more a sign of how change-resistant network television has traditionally been. But whether the Leno decision stemmed from desperation (by most gauges, NBC is now the fourth-ranked broadcast network), PR bravado (this is show business, after all), or just an unsentimental recognition of the need to make lemonade out of lemons, it will be only the first of many such moves. Amid an economic downturn that’s calling into question most old-school business strategies, the underpinnings of much of the mainstream television business are coming unstuck—and the first casualty may be the profusion of triple-decker, lavishly produced, scripted television that we’ve all taken for granted.