I noticed something very interesting.
Here is a link to the stats (pageviews, new posts, new topics, new members, etc. on a monthly basis):
http://catholicforum.fisheaters.com/index.php?action=stats
What I'm really paying attention to is the column of new posts. You'll see that beginning in May of 2009, going all the way to March of 2013, FE was getting more than ten thousand (and averaging, at a cursory glance, probably fifteen thousand) new posts per month. There is one anomaly in that stretch of March 2012, though I think that can be explained easily by Lent.
After March of 2013, there is a marked decline (spanning seven months, until now) in new posts. Definitely not an anomaly, but a clear trend. What happened in March of 2013? Well, I know that's when I was banned. But that's when Francis was elected. Is that also when Impy "came out?" In any event, when April 2013 rolled around, FE was on a clear down trend and has continued thus.
Now, the actual page views have not suffered, though I think that can easily be owed to FE being discussed here often over the last six months.
It says they've had 349 users on "today" -- does that count guests? Right now, FE has 290 guests and 22 users online.
The number of members that have logged in within a 24-hour period is probably the best metric for the activity level of a forum.
For example, CathInfo usually has around 180+
members online within a 24-hour period. (I have a script that tells me this, complete with a list of which members!) It's hard to count or even consider "guests", since they could be anything from a search engine to a bot in China.