? Throughout its history, public broadcasting in America has been a medium in search of a mission. It was born during the early 1950s as an attempt to harness the educational potential of the "electronic blackboard." It was revamped during the '60s as an institution designed to preserve and foster America's (and, cynics would add, Britain's) "cultural heritage." Over the course of three decades, public broadcasting has received lavish praise, pointed criticism, and more than $...