The last time you bought something, did you use a card, cash or something else? If you automatically thought "who uses cash nowadays", you're far from alone. More and more people are eschewing physical currency for digital dollars, and this move seems largely supported by big banks as well some countries. Proponents argue a cashless society has no shortage of benefits for everyone involved, but critics suspect there are more than a few dangerous possibilities at play -- and something sinister may be afoot.