Many companies build up their inventory levels to:

Accommodate for uncertainties in demand;
Take advantage of economies of scale;
Accommodate for unreliable suppliers;
Accommodate for quality issues;
Accommodate for production and scheduling errors.
Yet, JIT and Lean Manufacturing philosophies state that inventory is considered waste and should be eliminated as much as possible.

Please make a post which makes the case for building up inventory levels.
Please make a second post which makes the case for using JIT & Lean Manufacturing to eliminate as much inventory as possible.
Please make a third post in which you choose a company (or industry) and discuss which of these inventory methodologies you would follow and why.