The introduction of cable systems into the nation's urban centers presents almost equal measures of promise and peril to potential builders of such systems. The opportunities and needs of urban centers present a direct and welcomed challenge to cable system advocates almost everywhere. Communications, in general, and cable, in particular, have long been heralded as the means toward such broad and laudable goals as better understanding among citizens and improved urban living. The magic of words like "interactive" and "two-way" simply quickens the excitement; almost by their very mention alone.