A cavernous 10,000-square-foot medical marijuana emporium is set to open in California, and in coming months the company behind it plans to open similar stores in Arizona, Colorado, New Jersey, and Oregon. The new weGrow store - which wags have dubbed the "Wal-Mart of Weed" - isn't selling medical marijuana. It's offering up how-to experts and merchandise to help medical marijuana patients grow pot hydroponically.