The only reason a smart person would want to work there is golden handcuffs. There must be something material ($$$) that most long time employees get there. Or they are not smart. Slaves did not have a choice to quit slavery. People under Mao or other communism regimes could not quit also. Pyramids were build presumably without forced labor...but you got gods' blessing. Manipulation and promises go only so long (hence attrition rates?). But given some products coming out of amazon (Fire Phone anyone) I have doubts there are many smart people left at Amazon.
Perhaps TFA misses something?