This is an interesting post because our local Pagan Meetup.com page recently shut down due to this. We had a core group of maybe 10 that did stuff, about another 10 that showed up once or twice a year, but around 200 people on our Meetup. It was very disheartening and we finally determined that what we were offering was not of use to the community. They had found other ways of participating/finding community (and the snarky part of me says they found easier ways that didn't require their actual participation - if they only wanted a congregational experience I know a nice mega-church down the road... grrrr).
But my point is that we did try first thinning out people who hadn't come to any event in over two years and also asking people to give us feedback as to why they weren't coming, etc. The good of it is that we figured out what need wasn't being addressed, what the core of us who did participate wanted and were able to discard the useless bits and our core group is far healthier and happier for the dumping of the excessive weight that was the Meetup. I think lurkers are all well and good - I'm not shy when it comes to public interaction, but a lot of people are. However, narrowing down the membership to actually active folks - maybe by number of log ons within a certain period (if they haven't logged on since they created their account a year ago, for instance) might allow the board to focus more on the needs of those actually participating.
The caveat to that is that the posts on the board that are old are a great resource to read through, even if the person who posted it hasn't been on in a year and a half!
