I've been saying it for a while, but never really put hard evidence to it. Our community has declined and by the numbers I'll produce, I'm going to say it declined a lot. I just wrote a quick shell script to parse the number of messages posted to each given list (cooker, expert, and newbie) since 2003 (takes the total for each month and adds them together to get the yearly total). Of course, we still have 3.5 weeks in December, but I doubt that will make the numbers any more "impressive".
Of course, to put things into perspective, some of this has likely been off-loaded to the Club forums. I have no idea how many posts are there and how they change from year to year. It also looks like 2005->2006 was extremely significant, but my memory is hazy and I don't remember what happened there (well, I'm too lazy to try and figure out what happened there... something negative anyways).
EDIT: Well, a few comments have put this more into perspective, especially for the cooker list. Anne reminded me that all the bugzilla mails used to go to cooker@ and they don't anymore (having the bugs@ list). That accounts for the massive drop in "activity" on the cooker list. And it seems like forums are becoming so much more popular that the mailing lists are dying as a result (not necessarily a bad thing, but at the same time... maybe shut down the "support" lists and go for a straight-forum model?) Anyways, I'll leave the numbers up as food for thought, but it's not such a "sad metric" as I first said. My bad. =)
For cooker, the main development list:
For the expert list, which is a community-driven support list:
And for the newbie list:
Something else to chew on.