Its success of late is largely predicated on free shipping to customers, which everyone knows is not free to AMZN.
Brick and mortar retailers don't depend on low shipping costs to customers to the same degree. When oil rises again, AMZN's model will be the one needing to adapt or die. People may like to order online, but if they have to pay $10 extra to do so, that may change the equation.
The company has real estate and buildings that are carried on the books at cost minus accumulated depreciation. The difference between the value on the books and fair market value is billions of dollars. All the property is unencumbered.
With a market cap of $6.5B, the stock is trading at a 35%+ discount to the value of the real estate and buildings alone. Then there's the $4B in inventory, $423M in cash, etc. The company's debt is all long term with none of it coming due before 2021.