Activity has always been a problem iirc.
It's due to two main factors, imo:
1) Small (diminishing?) pool of people to pull replacements from, and
2) Negative externalities (the more people are inactive, the more people have incentive to be inactive... like the reverse effect of social networks).
There's not much that can really be done about the first one, other than advertising (which I don't think is really correct or moral to do? idk). There's also not much that can be done about the second one, because it's a coordination failure with large external forces (finals, holidays, etc.) other than somehow getting people really motivated to play. Currently, we have a lot of games in the queue, which aren't progressing/filling up at a good rate, mostly because it's "more fun to make a game than to play it", generally speaking (it's more engaging, etc etc). And while I am sure most, if not all, are fine games, a lot of people just don't have the energy/time to commit to most of them. A few really stand out as "everyone wants to play" (BYOR-style and other hectic games, games from GM's who are regarded as great... those generally intersect, too).
Main point: It might be best for the subforum if people didn't run games which there is little demand for. It might be a bit (very?) annoying for people who are on the current queue, but it seems that there is little sense in running games which people can't find time to play, or which take forever to start due to just not enough people. This could also be due to setups which are really big in general, and not us having enough people, now that I think about it, but...
I believe this is the uncomfortable truth. No idea of how, or even if, this should be enforced or self-enforced. I might have an incorrect view on the subforum's activity, as I haven't played any games recently (the usual excuses of finals and such, except that you don't have to find a replacement for me
), so correct me if this is not so.