First, Google got into same-day delivery service, and now Walmart is using its own customers for speedy online shipments. Apparently, the new delivery program from Walmart enlists shoppers in Walmart's physical stores to deliver goodies ordered by Walmart's online shoppers.
This sounds super-weird, but in fact isn't much different from TaskRabbit or Relay Rides or any other crowdsourcing-based model, for that matter. It's about creating a new marketplace by connecting supply and demand in a simple, cost-effective way.
Walmart's always been a big saver, so it probably figured that it can cut its transportation and delivery costs by employing its own customers. Second, economically disadvantaged customers will probably show up at stores more often for the prospect of earning a discount. For everyone else, the result may be increased brand affinity due to sustainability and efficiency factors of this solution.
Besides, retailers big and small have started a race of the fastest possible delivery to customers, as they understand that, in the midst of product commoditization, this can be the source of their competitive advantage.
I'd love to enjoy this idea for a bit more now, before starting to think about everything that can go wrong with it (tardiness, fraud, regulations, insurance).