MasterCard opens up a new front in the battle for e-commerce dollars with Free Shipping by MasterCard, which offers free two-day shipping at five top retailers when subscribers use their MasterCard debit or credit card for online purchases during a six-month complimentary membership; for $69 a year, cardholders can enjoy the same service at 30 popular retail websites. All Things D examines the program, which Clarus built and manages.