Someone who consumes wiki content but does not contribute to it by adding tags, comments or refining content is considered a Spectator (or sometimes Consumer or Lurker). This is an important EntryLevel role.
A healthy wiki is, at it's essence, a knowledge repository. It is fair and safe to assume that some members of the community, perhaps a large portion, simply need the information in the wiki but don't generate any new information or insights on their own. This is an important precursor to a Contributor as these people already understand the value of the resource itself, and it may be only a matter of time and encouragement before they will want to contribute their own thoughts.
A spectator may be a manager or a colleague from another group which has nothing, at this time, to contribute, but comes to your departmental wiki frequently to get phone numbers or group member names, other needed information.