What do Data Privacy Settings for Accounts control and what is the setting used for?
Each account has a Data Privacy Setting. The data privacy feature allows an administrator to open specific accounts so that the values of those accounts are usable within formulas written by users on other levels. This setting is intended to prevent users from writing a formula to reference data they should not have access to. For example, we would not want a user who only has access to the Sales level to be able to write a formula to reference the value of the Salary account for the Finance level. When a user attempts to create a formula that references the value of a private account at a level that is not its child, the user will receive an error that states "This formula refers to a level that cannot be referenced from this level,". The data privacy choices are:
Value of account is private (this is the default)
Private Accounts prevent a user on one level from writing a formula to refer to the value of this account on another level unless the other level is a child of the current level. This is the standard setting for all accounts.
So, a formula can be created in a parent level level that references data from its child levels without having to adjust Data Privacy Settings.
Value of account is public at corporate level only
In accounts which are public at corporate rollup only, formulas on any level can refer to the value of that account at the Corporate Level rollup level, but cannot refer to its value at any other level level (except, as with private accounts, for levels beneath the current level).
So, in order to reference data from the Corporate Level in any of the lower levels in the level tree, the data privacy settings must be set to "Public at the Corporate Level only".
Value of account is public at all levels
In accounts which are public at all levels, formulas in any level, including a rollup level, can refer to the value of the public account in any other level, regardless of whether the level containing the formula is over, below, or related in any way to the level being referenced.
Data Privacy does not apply to Assumptions, which function as though they were "public at corporate level only."