Although a cost-leadership strategy provides some protection against the five forces, it also carries some risks. If a new entrant with new and relevant expertise enters the market, the low-cost leader's margins may erode due to loss in market share while it attempts to learn new capabilities. For example, Walmart faces challenges to its cost leadership: Target has had success due to its superior merchandising capabilities. The Dollar Store has drawn customers who prefer a smaller format than the big box of Walmart. The risk of replacement is particularly pertinent if a potent substitute emerges due to an innovation. Leveraging e-commerce, Amazon has become a potent substitute and thus a powerful threat to many brick-and-mortar retail outlets including Barnes & Noble, Best Buy, The Home Depot, and even Walmart. Powerful suppliers and buyers may be able to reduce margins so much that the low-cost leader could have difficulty covering the cost of capital, and lose the potential for a competitive advantage. The low-cost leader also needs to stay vigilant to keep its cost the lowest in the industry. Over time, competitors can beat the cost leader by implementing the same business strategy, but more effectively. Although keeping its cost the lowest in the industry is imperative, the cost leader most not forget that it needs to create an acceptable level of value. If continuously lowering costs leads to a value proposition that falls below an acceptable threshold, the low-cost leader's market share will evaporate. Finally, the low-cost leader faces significant difficulties when the focus of competition shifts from price to non-price attributes.