Same-day delivery services (think Webvan and Kozmo) crashed and burned in 2001. But a new crop of start-ups claims this time is different. 

Why It Might Work

Today's GPS-enabled smartphones can track couriers and goods much more efficiently. More important, fleets of vehicles and professional drivers are no longer required. Start-ups such as Deliv and Postmates crowdsource that work to a pool of vetted part-time drivers.

"That's the disruption," says Daphne Carmeli, CEO of Deliv, which is running a pilot in San Francisco and Chicago in which retailers foot the delivery bill. Postmates, in San Francisco, Seattle, and New York City, charges consumers $6.99 and up for within-the-hour delivery.

Why It Could Flop... Again

The competition is stiff: Amazon, Walmart, eBay, and Google all either are in the game already or will be soon. To survive, start-ups must deliver reliably (no easy task) at a price consumers will accept--$5 to $10, says Kris Bjorson, a retail expert at consulting firm Jones Lang LaSalle.