Organisations use DCE for a variety of reasons: some use it to write large, secure, distributed applications. Many others use applications built using DCE or toolkits based on DCE. Some examples of these are:
DFS: The Distributed File System. Based on the AFS but using DCE/RPC and the core DCE services. DFS provides a single image of a secure, scaleable, reliable file system that can be distributed across multiple servers. Data can be replicated across multiple servers for performance and availability. Caching by the client provides good performance.
Encina Toolkit, Encina Monitor and CICS/6000. Transarc's Encina Toolkit builds on DCE to provide Transactional-RPC and other services required for Distributed Transaction Processing. The Encina Monitor provides the environment for building and administering Encina applications. CICS/6000 is a re-implementation of CICS which uses the Encina Toolkit.
ComponentBroker. IBM's CORBA-compliant Object Request Broker is based on DCE and uses DCE/RPC for communication as well as DCE's security and directory services.
ACMS/xp. Digital's Transaction Processing Monitor is based on DCE. The original ACMS was VAX-based.
The organisations that use DCE tend to be large, distributed and concerned about the security of their application:
Telcos and their suppliers. BT, C&W, Orange, Nortel, Alcatel, Bellcore, Ericsson, Nokia, TeleDanmark, ...
DCE is used to control switches (exchanges) and for dealing with the billing information generated, as well as related applications.
Big banks. Barclays, NatWest, CitiBank, Chemical Bank, First National Bank, ...
I'm pleased that banks want to protect my money.
Large Government departments. DSS/Inland Revenue, Ministry of Agriculture, Belastingdienst (Dutch Tax Service), ...
I'm pleased that governments are being careful with my money.
The military. NATO, Ministry of Defence, Department of Defence, the Danish, Norwegian and Swedish armed services, ...
I don't want to know.
Academia. Many large universities in the USA use DFS to provide a consistent access to the filestore of the entire university. The large users in Europe are Chalmers University of Technology in Göteborg, Sweden and the University of Stuttgart.
Many others. Consignia (The Post Office), Transco (British Gas), the RAC, BA, Nederlandse Spoorwegen, Deutsche Bahn, Scania, ...