I don't think fansubbing is a good way to go to bring in forumers, unless a few people are willing to make it an unpaid fulltime job to be faster/better than everyone else for at least 2-3 cours. In fact, bringing people to GW was never the primary motivation of the creation of the group (that would obviously be unsustainable, especially for three years), but more a hopeful side effect.
The most successful site/forum combos I've seen that don't create their own content have some unique systemic advantage over the other sites - Like Manga Traders or Haruhi Chan (or MAL, ANN, etc).
GW had the niche on a few popular/mainstreamly hyped anime like Mirai Nikki and Sword Art Online (with UTW), but yeah. Discussing these shows in a centralized hubbub trumps a place like this unless you put in some hardcore work, I think. Also, at this point none of the staff in the group were actual forum members except me, so getting everyone to market the forum as much as possible other than a link in the navigation would have been troublesome. It would also take some sort of hyper motivation on the forumers part to join a place where they're likely to get bullied or hazed by someone retarded (like Arch).
Or, someone could animate an original anime! Or create a manga~
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Some failed attempt at creating a scanlation group by Arch .