#conferenceid should be a short and unique id used to identify the conference where you are presenting.
Examples of this are #pdc08 and #teched or #tela09 (for TechEd 09 Los Angeles).
The audience DOES NOT need to add this hashtag to the feedback they sent, it will be used in messages sent by Demo Dashboard and only in a few ones like the Session Starting and Session Ending notices so anyone following the conference hashtag can read when
sessions are starting and ending.
If you're presenting in a conference that doesn't have its own well-defined hashtag by the community, just get creative an invent your own! :)