SQL Server Table Design for Report - Is OLAP Schema Suitable
For databases of a significant size, the normalised logical design is typically created first. Following this, sample queries are run and the database is then denormalised for performance if need be (the physical design). If the gains are minimal, you may elect to stick with the logical design for the simple reason that it is easier to understand and is more efficient from a storage point of view.

It would be somewhat presumptuous to go for a denormalised design from the off without any sort of performance testing - even if this is clearly an OLAP system.