Are any of the practical implementations of ORAM being used in a real world system?
In addition to Paul's answer there is even an ORAM module inside a processor architecture, fully implemented: “A secure processor architecture for encrypted computation on untrusted programs”

Abstract:


  This paper considers encrypted computation where the user specifies encrypted inputs to an untrusted program, and the server computes on those encrypted inputs. To this end we propose a secure processor architecture, called Ascend, that guarantees privacy of data when arbitrary programs use the data running in a cloud-like environment (eg, an untrusted server running an untrusted software stack).