Data Warehouse and Business Intelligence (DW/BI) implementation is frequently considered a black hole for the IT budget. It is hard (almost impossible) to run a business without one, but requires substantial investment to reshape your existing transactional systems to clean “dirty” data, fix existing (but broken) business processes and formalize analytical needs for different departments. Vast majority of these costs have nothing to do with the Data Warehouse, but become noticeable during DW/BI project.
My team at GRT Corporation has deployed tens of Data Warehouses for Fortune 50, as well as smaller size companies. One of the most common challenges for DW/BI implementation is loose definition of business requirements by the business. This is not something that can be fixed, for a simple reason – it’s very hard to tell what you need for the system until you start using it every day. Good Data Warehouses are built in phases not because the scope is huge, but because user requirements are changing while the business is getting hands-on experience analyzing real data.