Activity
I have already stated that activity and substance or an integral part of cyberspace. But why?
Well, consider the before-mentioned chat room. Once again(or maybe for the first time depending upon your choice of links), the substance, the chat room, is dependent upon the users' activity. Simply being virtually present (observing the room) does not constitute cyberspace. It is the interaction of the participants and their "bits" on information that constitutes cyberspace.
This is different from an atom-based room consisting of literally present individuals. Here, the substance (or Cyberspace) could be their simple presence, their conversation, or both.