"Mothers of America, let your kids go to the movies!" Always good advice, but the exhortation has dated a bit since 1960, when Frank O'Hara made it the first line of his poem "Ave Maria." "Going to the movies" has a quaint ring in the age of the plasma-screen home entertainment system, the iPod and video-on-demand. The movies are more than willing to come to us, which has inspired some sages, in and outside the film industry, to prophesy the obsolescence, or at least the increasing marginality, of paper tickets, bags of popcorn and big dark rooms lighted by a projector beam: the cultural ritual known dispassionately in the business as "theatrical distribution." A.O. Scott reports.