>Horses are tools that people used. When there's no more use for the tool, it's usage may be reduces. People are not just tools, they are the reason we have an economy in the first place. A solution in some form will have to be put forth if one doesn't emerge.<

I'm unsatisfied with the ubiquitous horse analogy as well. The economy exists to solve human problems, not horse problems. We are constantly generating new problems and new social performances. It would not surprise me if the economy of the future was based around elaborate, manpower-intensive tea-ceremony-like rituals or something equally preposterous. Human obsolescence is not inevitable, but might be engineered.