Depends on the area. Walmart's Data Warehouse is one of the best out there and pretty much everything they do, including product placement, ads, etc are done by the Data Warehouse:

[link to en.wikipedia.org]

Benefits of a data warehouse

A data warehouse maintains a copy of information from the source transaction systems. This architectural complexity provides the opportunity to:

Maintain data history, even if the source transaction systems do not.

Integrate data from multiple source systems, enabling a central view across the enterprise. This benefit is always valuable, but particularly so when the organization has grown by merger.

Improve data quality, by providing consistent codes and descriptions, flagging or even fixing bad data.

Present the organization's information consistently.

Provide a single common data model for all data of interest regardless of the data's source.

Restructure the data so that it makes sense to the business users.

Restructure the data so that it delivers excellent query performance, even for complex analytic queries, without impacting the operational systems.

Add value to operational business applications, notably customer relationship management (CRM) systems.

Now let me be clear: This is not new technology we've had it since the late 80's publically.