"Forumitis" is something that's been tossed around here a bit, but I think it's worth talking about in the general sense. Not all forums are subject to forumitis, but most of the large, well-known ones tend to be. It doesn't happen because they're dumb, or because there's anything inherently wrong with forums (although, as we'll discuss, it is a natural consequence of their popularity), or any other conveniently self-justifying explanation. It's human nature in action, and no more.
First, though, what is forumitis? It's not easy to pin down, but I think my definition, at least, would be "errors in game play and conceptualization that are reinforced by the mass of people contributing." It's not that blogs, etc, don't make mistakes and don't get things wrong, but the nature of forums tends to make these problems self-reinforcing.
Second, why do we care? I, at least, care because I don't like bad information. When someone says "Fire Warriors are good," it bothers me because that isn't really true. And, as both Kirby and VT2 have pointed out, convincing people to buy mediocre units thinking they are good ones is not a way to encourage goodwill towards the hobby- it leads to frustrated players, who may quit the hobby because they see their army as being unsalvagable or the game as unbalanced.
So why does "forumitis" happen? I doubt many of you have studied the dynamics of social interaction extensively, but to sum things up, it's because they get too big. As the population of a forum grows, the ability of the members to monitor and correct each other's behavior deteriorates; whereas in a small forum everyone knows each other and poor courtesy doesn't last without severe social consequences (like getting on EVERYONE'S ignore list), as the size of a group (real or internet) grows it becomes more difficult to self-monitor. In real-world groups this normally results in splintering into subgroups; on the internet, it just as commonly results in a large, directionless mass of users with few clear social boundaries. At this stage the moderators are likely to become strained and simple enact strict rules regarding what can and cannot be said, drastically limiting the ability of the users to engage in effective discourse. With no strong method to argue and reach conclusions in a meaningful way, opinions will generally settle into their respective position, and you're left with a morass of mediocre ideas punctuated by extreme outliers that may or may not have any bearing on reality. Those of you who have read about the "Eternal September" will recognize the same progression there, and in the evolution of many other social contexts.
Does this sound familiar to anyone? Plenty of 40K forums have gone down this route, not to name any names. Personally, I cannot name a single forum that I think is host to good and relevant discussion about gameplay and tactics. (Painting/modeling, on the other hand, are a different matter, since they are largely a matter of putting forward examples for others to study. Even resoundingly mediocre forums can be host to good hobbyists, and hence worth studying.) Of course, this isn't to say that they don't exist- but, by the very nature of the system any good forums would generally be small enough to escape the radar of most people, myself included.
Why are blogs any different? Different modes of interaction. Blogs are not democratic- they are inherently biased, focused on the owner(s) of the blog; while followers and others may comment, their contributions are subsidary, not the focus of the thing. Those with good and popular ideas will generally flourish; unpopular, poorly-written, and poorly-conceived posts will drive people away. In this way someone with strong ideas is able to shape a community to a degree, and while popularity is certainly no measure of correctness, I do like to think that people are more likely to follow a good idea than a bad one, human fallacy aside. Blogs exist as interconnected networks, not as a single, massive entity, which shapes how users join and participate very differently. While they may be prone to problems of their own (demagoguery, interpersonal drama, etc), these are very different issues with their own kinds of solutions.
It's not that I have anything against forums; I think they potentially have many uses and can bring some very useful modes of communication. If they have a good community, they are a much easier way for people to reach out for assistance, rather than Kirb or I having to sort through dozens of similar emails. However, they too often fall into the traps that bring them down to a level that is no longer particularly useful, the worst of which being the "everyone's ideas are equally right, no matter what" paradigm.
If any of the readers would care to suggest a counter-example to the above, a good forum with a large population, I would be happy to be wrong. Unfortunately, most of the forums I have visited have ended up being fairly useless to good discussion- and make no mistake, I have seen quite a few of them. Advanced Tau Tactica, Warseer, 40KOnline, Bolter & Chainsword, Dakka Dakka, HeresyOnline, etc. I mean no insult to the people there- indeed, there are at least a couple people at each of those forums that I respect, if not always agree with, but that doesn't mean that they make discussion easy or possible; after all, it's hard to talk about proper deployment strategies when there's still someone who is insistent that Servitors are a good unit if you give them a chance.
