There isn't much real functionality around account hierarchies. It's obvious that Salesforce.com wasn't really designed for real global account management where a company has many subsidiaries with many account managers.

For one thing you can't report on opportunities owned by an account hierarchy. You can report on opportunities that share a single parent account -- BUT the parent account itself's opportunities can't be included in there.

It gets even worse if an account is the child of one account and the parent of another account. The odds of being able to ever get a global picture easily fade even further.

When you have multiple account managers managing various subsidiaries in an account hierarchy, you can't give them read-only permissions to the opportunities in the other subsidiaries he doesn't own without really trying to be clever with sharing rules, or by assigning the sharing rules manually.

This could really get clunky for an account with dozens of subsidiaries, considering if you are like us, you might have many of these types of global accounts.