Data warehouses are a lot of work. Once they are built, they cost money. They need to be monitored. People are constantly requesting changes and additions. The cost of storage quickly adds up. But the real difficulty of data warehouses comes in the transformation. Older applications have to be merged together when they were never designed to be merged. Definitions of data are confusing. Merging older technology is a real challenge because there simply are not people with skills available that understand the technology of yesterday. There is scant documentation, and where there is documentation, it is out of date.