This holiday shopping season some people may be leaving their wallets at home but still spending plenty. The new mobile payment apps like Google Wallet and Square allow people to pay with their phones. For now only certain phones and a limited number of retailers allow these methods of payment but it looks like the trend toward paying by phone may be here to stay. So do these apps mean the end of cash? How well do they really work? And, how will paying electronically affect our spending habits? Marty’s guests are Wall Street Journal technology columnist KATHERINE BOEHRET and Duke University behavioral economist DAN ARIELY. We’ll also get tips on how to avoid banking fees from GREG McBRIDE, senior financial analyst with Bankrate.com.