Object UUIDs are often used in the DCE RPC binding mechanism. The details of RPC binding are explained in Registering the Server, and more thoroughly in Binding. It all comes down to this: clients import only partial bindings from the namespace. These will carry them only as far as the endpoint mapper service of the dced on the destination server's host; it is dced's job to resolve the binding with a dynamic endpoint.
This means that some registration of bindings must be done by a server with the endpoint mapper. The minimum two items that have to be registered are interface UUIDs and bindings (the latter of which contains the server's dynamically allocated endpoints). With this information available, the endpoint mapper can inspect the incoming RPCs interface UUIDs, select one of the endpoints that was registered under them, and resolve the partial bindings. In addition, a server can register its object UUIDs with its endpoint mapper. This allows lookups of endpoints by object UUID rather than interface UUID; the advantage is that object UUIDs are much more specific than interface UUIDs, which may be registered by multiple servers at the same host.