Hi David,
Citizendium has a community of writers and appears to be ticking along okay.
Unfortunately, more than a few appear to be driven by resentment of Wikipedia, and by far the most effective method of getting publicity so far has been to bitch about Wikpedia (the "let's you and him fight" story is one beloved of lazy journalists everywhere) - which makes CZ look less than classy (less classy than it is).
Epistemia, from the description, appears to be yet another thing in the same space. What's the differentiator from Citizendium?
I'm working on a FAQ at the moment. You can see the current version (which is a real draft) at http://en.epistemia.org/wiki/Epistemia:Frequently_asked_questions. Basically, my notes (which need to be expanded upon) are that Citizendium:
* is overly restrictive; * is not very dynamic or global; * has failed to gain significant public support, after over two years of operation; * has not been growing exponentially; instead, growth is a "straight line"; * alienates people by requiring all contributors to use their real names; and * is a knee-jerk reaction to Wikipedia.
Epistemia basically addresses these problems by being unbureaucratic, having a low barrier to entry, and being more globally-orientated.
—Thomas Larsen