How to log and display all the users that have edited a node (without revisioning)?
The Activity module does some user activity logging that may covert your need.


  The Activity module keeps track of the things people do on your site
  and provides mini-feeds of these activities in blocks, in a
  specialized table, and via RSS. The module is extensible so that any
  other module can integrate with it. The messages that are produced are
  customizable via the admin interface and are context sensitive. Some
  theoretical example messages include:
  
  
  You wrote a comment in response to "example comment title"
  Jim wants to be your friend. Approve this friendship here
  Nancy is Phil's latest fan