EMC has entered the data warehouse appliance market via the purchase of Greenplum, who made good progress in the space with their massively parallel database (based on PostgresSQL). Greenplum had impressive reference customers and some of the highest end references out there in terms of sheer scale of data. They had also been one of the few vendors (Aster is another) that went early into embracing MapReduce, a framework designed for paralleism and suitable for certain types of complex processing.
Data warehouse appliances can be a tough sell because conservative buyers are nevous of making major purchases from saller comapnies, but the EMC brand will remove that concern. Also, EMC have a vast existing customer base and the sales channel that can exploit this. Seems like a sensible move to me.