In reference to this Linden Answers thread
I own a vbulletin liscense - you can specify a forum to allow just the person who opened the thread to reply, and allow certain users / usergroups to as well. I think that would be the ideal solution, allowing people to give extra information etc in once place, meaning archived versions contain all the details if someone else has the same question later on.
[edit]o.O Thread id 100000[/edit]