How Many Versions Of My Data Do I Really Want?

I got into a bit of a disagreement with someone today over the idea of Pre-Aggregation of data before bringing it into PowerPivot in Excel as opposed to bringing in all the source data for all the tables to be analyzed and then doing all the necessary aggregations exclusively in Excel using PowerPivot.

Let me make it perfectly clear that I am not pleased that there has to be a disagreement .. the fact that it looks like it is becoming one is sad.   Unfortunately I feel the need to aggressively promote what I believe is true because there are people who are in my opinion limiting the prospects for PowerPivot and Excel by their promotion of a limited vision for PowerPivot.  I know in their hearts they believe they are right – But I beg to offer an alternative view.  I believe that those who do not share my…