It might be costly, but as more big box retailers offer same-day delivery, free shipping will eventually become standard across the e-commerce landscape. 

The fact is, consumers will simply demand it, wrote Ad Age's Lauren Sherman. E-commerce is big business—and expected to hit $327 billion by 2016, according to Forrester Research—which means "same-day delivery shipping services are changing consumer behavior—and fast." 

Though retailers "have flirted" with free shipping for years, Sherman says they'll really have to "pony up" if they're determined to keep their business. And they will, because as the arena gets more competitive, they won't have much of a choice. 

[via Ad Age]