If the concern if for non-member attendees being displayed, what if a preference questions could be implemented right into the registration form itself? Further, this would allow members to choose event-by-event which they would prefer to publish their attending status.
We would greatly benefit from this feature. For many of our events, we publish attendee rosters so people can coordinate hotel rooms, car pooling, etc. We also publish rosters of vendors and exhibitors who have registered to attend. Right now this is all being done by hand through PDFs. Having a live, dynamic list would be very useful.
I completely understand the privacy aspect, but I believe having an opt-out (or if really paranoid, an opt-in) in the registration form itself would solve that problem.