CL quotes Chin Huang: "The Running Object Table (ROT) is a globally accessible table listing objects running on the system. This table only lists the applications that registered themselves in the table, but the major Windows applications do so." Part of the point is that ROT enumerates what's visible to tcom.
Example code for introspection on the ROT appears at http://www.alexfedotov.com/samples/enumrot.asp .
CL has been thinking about how it'd be nice if tcom knew to do the same ...