As a customer I do not mind using a forum for support but most times I need something that requires me to open a ticket. If it is a general question then a forum is fine. If it is like downgrading my account or upgradding my account or related to my account then a ticket is better.
Also as a customer, specially a potential customer. If I am looking at your site to maybe host with you and see that the forum is dead I might think the host it self is dead or dieing and more then likely will not be setting up an account.