Forum for support is not good. Forums are for grievances, Comments, Announcenets, ideas sharing and discussions. Also, prospective clients evaluates your services based on forum activity and replies.
We did an experiemnt.. kept a section of forum for "Customers Only" and it proved to be a great success. If customers have any problem/concern they can easily post there and we took that issue on priority.
For support we put a separate system in place (Cerberus HelpDesk) and we encouraged our clients to use that if there is no urgency.
Support request can be of three types..
1) Urgent (Site Down, Email etc.)
2) Regular (permissions, DB restore etc.)
3) Delayed (when support take extra ordinary time in replies).
For 1st live-chat/phone is good. For 2nd Tickets/Support Helpdesk is good. For 3rd Forum is best.
So, Forum is essential, whether you use it for support or not.
Hope this will help you to design your support system
