This is interesting on several fronts.
First, for those 20 cities still vying for the second AMZN headquarters, it represents a risk. A huge employer in a geographic area that cuts a high number of jobs can create a lot of problems for the area. Be careful for what you ask for!
Second. Usually when companies expand too quickly there is always hiring that was inefficient. Too many employees for the work to be done result in work force reductions. The quick ramp up and then ramp down will cause inefficiencies as employees who remain will often refocus from expanding the business to doing things to protect their jobs. AMZN has been expanding really fast.
Third. AMZN has created huge momentum in the "retail" market. Retail often relies on consumers' habits. You get enticed to buy because of "sales". Once you have established a habit of buying in a certain way, prices usually rise and the consumer does not re-evaluate the purchases they did previously. Is the service going to degrade or are prices going to rise? I don't know but retail sales are clearly based on habit.
Whatever companies you like, you must understand both the upside and downside attributes! Always look carefully and understand both sides of the coin.