(How) Has Open Source Data Warehousing Developed?

Given the strengths of open source database management systems (DBMSes), open source seems like a natural platform for data warehousing. We’ve seen a number of success stories over the last few years, Travelocity, O’Reilly, FTD, and Frontier Airlines among them, but the roster of case studies is mighty thin. But I’ve only recently (re-)started looking  in the last couple of years, on the open-source front I’ve covered mostly BI (e.g., May, March)  and I hope to find many more for a report I am planning on open source (based) data warehousing (OSDW).