Which makes the case for building up inventory levels

Question

Assignment:

Many companies build up their inventory levels to:

1. Accommodate for uncertainties in demand;
2. Take advantage of economies of scale;
3. Accommodate for unreliable suppliers;
4. Accommodate for quality issues;
5. 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.

1. Please make a post which makes the case for building up inventory levels.
2. Please make a second post which makes the case for using JIT & Lean Manufacturing to eliminate as much inventory as possible.
3. 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.