I just left a Facebook support group. As with many, if not most online support forums, the administrators were terrible moderators.
Some members inundate the group with irrelevant messages. Recent ones from this group: a long discussion about members' frustration with Facebook Chat not presently working; some people posting things like "Any1 want to chat."
In another group I belonged to, a woman VERY frequently posted pictures of her child up in the group, inundating it. It was somewhat relevant in that her child was happy and active, with her condition, but still. A line has to be drawn. It's not a fan page for your daughter. The moderators disagreed that was an inappropriate inundation (any inundation is inappropriate, if you ask me) and a number of members defended the inundation. "I like the photos of X." Well, I like photos of cheese, but that doesn't mean they belong there. I have lots of photos me dancing ballet as a child, somewhat of a feat for people with my condition, but that doesn't mean I should post many of these photos, and do so periodically. Why should people have to see all that in their personal feeds or sift through it when they visit the group?
Spam. Spammers post messages and the administrators don't remove them. Sometimes, spammers block administrators, so that's fine, but in a closed group, new members have to get permission to enter. And it doesn't take a rocket scientist to see that they are spammers. There are also other things you can do to minimize spam, but that requires research.
Lack of moderation or guidance for people seeking medical advice, instead of support: "Is this serious? Is this because of the x condition?" or, my personal favourite: "Do you guys get this?" Because if other people in the group with your condition get it, that must mean that it's because of the x condition. This is faulty logic and an illogical methodology. It's bad enough when people publish these things, but worse when administrators condone it, or participate themselves. I got a cold last week. It must be because of my shunt. Also, doctors wouldn't even advise based on a Facebook post alone. A diagnosis requires medical history, a physical examination and tests. From a relevant doctor. Having the same condition doesn't qualify you to diagnose. Especially over Facebook.
Jerks. Numerous people post complaints about someone in the group being a jerk to them off-group, but the administrators STILL don't remove him/her.
I haven't visited these groups much. Fortunately, I haven't felt the need to, so it's not a huge loss, but it is a loss of an opportunity for me and others. Groups in general aren't a good opportunity to empower yourself; only well moderated ones are.