The Disney monorail system is commonly held up as a shining example of the technology in regular use. Despite the fact the system has never been truly successful other than a short-distance transit system (like Seattle's or many major airports') the monorail has been replaced in futurists' minds by electromagnetic and rail-based high speed machines. There are a few still under consideration and construction (operational in Mumbai, Seattle and Las Vegas and under consideration in Tennessee), but by and large other, grander, systems seem to have become the norm.
This is unfortunate, because as an image of the future, you really can't get more iconic than a monorail -- and for many of us, the Disney versions were the first we not only saw, but rode. And in a way, we touched the future.
(Taken in EPCOT Center, April, 2004)