Does your forum have any social media accounts? How often are they used? What do you post?
My forum has a Facebook page, Twitter, and Google Plus page. They aren't very active right now, but we're trying to get them running again because social media's a pretty good tool for advertising and gaining new members.
It used to, and then I never used it so I just ended up deleting it. I do not really see a huge point in using it, since the forum itself can be used as a social media (ish) platform as it is.
The only thing I can see it being used for is announcing something is wrong with the server, etc. Things you cannot post on your forum because well, the forum is down. Other than that I find it kind of pretty pointless.
Using social media to advertise your forum is a great idea!
I just started setting up a Twitter account for my newest forum to hopefully drive more potential people to my forum. It's a good way to get traffic but I've never really had anyone register from Twitter.
I have a Twitter right now, my members have asked for other social networking accounts too though so they can help spread the word - still need to get them set up. I don't tend to use the Twitter I have right now too much because I find maintaining it pretty hard, I would rather focus on my site. But Twitter has got me some key members so I keep at it.