This is the key word, "active".
What do you think drives this $ite?
When I started monitoring this site in 2007, I lurked for almost a year, until I joined in 2008 and became "active".
Since 2008, the "active membership" has grown at an impressive rate.
I can only assume the "lurkers" have grown at a similar or greater rate?
I'm going with greater rate.
Actual regular contributors is debatable, but the premise rings true, the active, registered users attract the "lurkers".
I look at it like the "Jerry Spinger Dynamic", the train wreck that they can relate with and cannot look away.
Either way, this site isn't a charity, it gets major play, or it wouldn't still be here.