Avis Walton is used to being told where to go and what to do once he gets there. As a "picker" for 99 Cents Only Stores, Walton spends his 5 a.m.-to-3:30 p.m. shift cruising around a 750,000-square-foot distribution center in Katy, Texas, in an electric cart responding to a stream of spoken instructions. "Go to row 12, section 8, bin 31," an authoritative woman's voice in his ear commands, and Walton zips to row 12. Blip-blip. He scans the bin tag with a wireless handheld computer to confirm he's arrived at the right place. "Pick two cases plus four items," the voice continues. Beginning t…
