How do you think about community "lurkers"? Is it worth actively converting lurkers to participants in an online community?
Inspired a bit by this comment on community health metrics, which brings up the nature of the role lurkers play in the community ecosystem.
If I had to pick one single health metric I'd go with pageviews. If those decline then you're either losing lurkers, or your regulars have fled and aren't posting anymore. That's the metric I look at on a daily basis. It's a bit of a lagging indicator, but at least it covers both sides of the creator/consumer spectrum and it's simple enough for everyone in the company to understand.