Multi-channel retailers and inventory management

There is a growing trend of brick and motor stores like Walmart establishing multiple channels including online and mobile purchases and online retailers like Amazon and Wayfair setting their foot on physical stores. Each has its own advantages and disadvantages in terms of inventory management. For example, Walmart in the recent times telling online shoppers that some products in its warehouses are "out of stock" in order to avoid the extra expenses associated with shipping items from farther warehouses and suggesting similar products that are available in nearest stores. Similarly, Amazon faces issues with Whole Foods by introducing online delivery of groceries especially perishable items like fruits and vegetables. Discuss some of the pros and cons associated with inventory management and control when introducing new channel for the retailers.