Porter's Five Forces

Considering Porter's Five Forces both domestically and globally, the focus seems to be on the “Buyer” quadrant and their bargaining power, but what is driving that power they have, and can a company mitigate that power of the buyer? Even if a company can mitigate that power do they really want to because it flows back through the supply chain giving them, an advantage/power where they might not have had an advantage/power before.