I am planning to add a forum to my blog, but before I make the leap, I have a question for the experts: Is it better to have the forum as a subdomain on the site (i.e. forum.thesite.com) or as a subdirectory (i.e. thesite.com/forum)? I've seen it both ways on successful sites, and I'm trying to figure out if one has benefits over the other. Thanks in advance.
I think subdirectory is better. subdirectory is considered as the same website because it is the same domain. This will benefit you main domain, because it will have more pages due to the forum. By using a subdomain, you are starting from zero
I agree with goodmast If you have many moderators frind and can make it run very succesfuly then only hink of running it as subdomain