I enjoyed this article primarily because I rarely use cash. I prefer to use credit cards for pretty much everything. Credit cards often have benefits programs (such as loyalty points, or cash back), and they also offer the ability to track your purchases and purchasing behavior quite easily. The flip side of this story is that it bodes well for alternative payment processing methods. For example, Jack Dorsey's company Square (which allows anyone to accept payments using an iPhone or an iPad) should bode well from the transition away from cash. We all know how popular PayPal is as a payment method and it operates completely cash-free. I imagine we'll always have a need for cash but it's interesting to see other payment methods receive more and more attention.
Interesting tid bit from the article: $100 bills have become a valuable export. When US soldiers raided one of Saddam Hussein's palaces in 2003 they found $650 million in fresh US $100 bills.