i too have yet to see it... i shop at three different Wal-Marts in the South Bay (San Francisco Bay Area, California) and have yet to see empty shelves... for the last three weeks i've been shopping at the Wal-Mart in Fayetteville, NC and have not seen empty shelves...
There are 5 W-Ms within a 10 mile radius of my house, 3 of which are within 5 miles of me. Only 1 is well stocked.
It’s an individual store manager’s problem, they are responsible for staffing, stocking numbers. Some try to maximize profit by not having adequate staff. Better profit, higher individual bonus.