Last I checked Beckett already has a forum, one that's about as content light as the magazine. And all the advertising stuff others have mentioned is already being done on their website, aside from offering "us" a special deal.
CU has a forum, and emails and whatever else. I signed up for the card emails and get the coin ones.

although I do sort of like the coin articles. Their boards aren't all that great, some content, but mostly "OMG WHY OH WHY ISN'T THIS CREASED CARD AT LEAST A 7?!?!?!" and stuff like that. (yes, an exaggeration, but not by much)
SGC has a board. It's not bad, but doesn't see much traffic.
Did GAI have one? Or is it coming Monday?
Having a message board that's relatively on-target, civil, and which has content and enough active members is vary hard. I'm on probably 4 of them and lurk on another. Two of those have really lost a bunch of traffic the last couple years. One because the guy running it sort of moved on to something else. The other because most of the experienced people who knew a LOT moved elsewhere mostly because the new guy wouldn't listen to the advice they asked for.
I don't think any of them actually make any profit. The one I lurk on might help the business of the guy who runs it, maybe.
Steve Birmingham