Just let the participants know that you will be away from your role for a specified period of time and what they should do during that time. Leadership often emerges in interesting ways in an electronic discussion. A short departure of the moderator can encourage leadership from participants. You will be able to read the messages from the discussion when you were unavailable and assess any problems that might need attention when you return. Stay aware of and assist the group process.
Time is a factor since people come and go in cyberspace at different times.
Also discussions are mostly limited to text and lack nonverbal cues. Moderators can do a great deal to facilitate group process on-line. Help the group grapple with the content. Participants have more time to reflect before responding to the discussion questions or to particular messages that have been posted. This aspect can be an advantage in dealing thoughtfully with the content.