I had a few spare cycles to do some reading recently, and thought I would check out the new Unified Dimensional Model (UDM) that can be used with Analysis Services 2005. I started by listening to a webcast by Amir and Ariel Netz. Interesting stuff about datamarts, data warehouse, and specialized metadata model proliferation. And the strengths of reporting against both relational and OLAP data. Although MOLAP cubes are still with us, AS2005 seems to be becoming a reporting clearinghouse, a "UDM server".
The only thing that struck me a bit strange was the concept of using live RDBMSs to feed UDM data caches as an adjunct to or replacement for datamarts and data warehouses. I've been spending a lot of time lately talking to DBAs who are concerned that features such as SQLCLR and in-database web services might blur the "focus" of a database, and make management more complex because of resource contention/sharing. I'd think that a UDM connection to a live database (rather than a reporting only database copy) might complicate management, sharing, and contention issues even more.
Reading more about this in SQL Server BOL, there IS a section on using database mirroring and snapshots to support reporting. So maybe they're not talking about a reporting connection to a live OLTP database, something that hasn't been done (with OLTP performance in mind) for a while. Maybe it's all done with mirrors.