Cash will never be obsolete until non-cash purchases can be made anonymous/paper-trailless. The black market is most likely 10%-50% of the market (depending on

Cash will never be obsolete until non-cash purchases can be made anonymous/paper-trailless. The black market is most likely 10%-50% of the market (depending on where you live, see http://en.wikipedia.org/wiki/Black_market#Comparison_with_regular_economy http://en.wikipedia.org/wiki/Black_market#Comparison_with_re...).