I'm not one for lengthy introductions, the title of the post brought you here, so let's dive in. Below are the aforementioned 5 problems, and I've attempted to provide a solution to help you remedy the problems. Would love to hear more from you in the comments or on Twitter.
1. You don't have passionate core members
The problem: The initial inclination when building an online community is volume. Getting those Follower counts high across your social channels seems to be paramount. And then after you reach an acceptable, beefy threshold - that's when you start to sculpt your community. Why is this? Isn't the "quality over quantity" concept well known by now? Why is this the place we compromise?
A solution: Take the time to identify potential members that already exhibit a passion for the topic around which your community is built. Reach out to them and tell them what you'd like to accomplish with your community efforts. They may be able to help with their own personal networks, and later help to organize the community. Putting a lot of effort into identifying these individuals up front will help when it comes to initiating community topics of conversation and having key agents for interaction outside of your company/org.
2. Your community manager is an outsider
The problem: You have a community of extremely well-versed and passionate UX designers (for example), and your community manager is just now learning about the importance of website wireframes. This doesn't mean she/he is bad at the job, they just aren't going to be fully aware of the potential to start conversations that ignite the community, or to see opportunities in community discourse.
A solution: Get your community manager a mentor. Or, if you are the community manager, find a mentor. The better you understand what your community is talking about, the better you'll be at doing your job. Warning: you will NOT be as versed as your community is in the topic at hand overnight, maybe never, but know enough to be helpful.
3. Is everybody welcome?
The problem: This 'problem' might not be a problem for some online communities, but if you have a niche community there is an expectation of common knowledge or being able to generate conversation at a certain level. Granting everyone access to a community may not be the best way to reinforce a community identity.
A solution: Condition different channels for different community purposes. Twitter is great for "anyone is invited" while a forum might be better for community access control. Setting expectations on each channel is how you can avoid isolating potential members, but also lets your community know that you're working hard to assure quality communication.
4. You haven't provided your community with a focus
The problem: You've attracted people to your community, but now they don't know where to start. Each community member has something that's important to them, even within your business's niche.
A solution: Provide a focus that is important to your organization and to the members of your community. Utilize a mentor, and the passionate user core to find a hot topic, and then you marry that topic to your organization's goals.
5. Your community members have weak relationships with each other
The problem: You've started addressing your online community as multiple two entity relationships, the member and the organization. There's a need for the organization, and a desire from the community members to interact.
A solution: Organize online and offline (if possible) events that require group interaction. Events with tasks/activities that require teamwork are especially useful in fostering inter-community relationships. A well-organized event allows for schmoozing and includes a structured group experience.
Notice that I've written "A" solution and not "The" solution. It's important to remember that our field is still new, and there are tons of ways that exist to fix any one problem, and you should mix and match until you find something that is useful for your community. And do the rest of your compatriots in community management a solid and document your tactics and strategy.
6. You're not acknowledging all forms of participation
The problem: As you build your community, you start to, perhaps unconsciously, assign interaction values to various forms of community participation. What this may lead to is discounting the potential of members contributing little, but still taking time to contribute. This dynamic is especially a problem if you're focusing too much on cultivating those who will make up the "power core" mentioned in the last post.
A solution: Power cores tend to make up the majority of community participation, but power cores also tend to make up a very small percentage of the membership. You might find that your community participation is divisible by three, the high, medium, and low. But "boundaries are fluid and one and the same member may shift from one level to another." - Etienne Wenger writes of community members' participatory fluxes. Potential power members may not seem that way at the beginning, they don't have time to post, they're temporarily busy or perhaps they grow into the role as they gain knowledge about your community.
7. You're too controlling, and inhibit community evolution.
The problem: Your business/you has goals for your community (you did set up goals, right? See: 10 if this is not the case) and your job may rely on you completing those goals. Your approach to the community is "they are here to serve my/my business's interests." While we all have jobs to do, part of the job is being aware that this may not (although, I'm sure in some communities, explicit boundaries to maintain focus are beneficial) be the best way to manage your community.
A solution: Allow the community to grow and evolve naturally. If you try and stop that, they'll leave. You'll need to align your business goals with the goals of the community, and not the other way around. It is much easier for you or your business to adapt than to change the natural ebb and flow of a group of people. With that being said: there is a careful balance to maintain between facilitating and dominating community management styles. You can't walk all over them, but don't let them walk all over you.
8. You haven't challenged your community intellectually.
The problem: Your community has stagnated in growth and activity because the conversations are too familiar. Perhaps the problem is that you've stopped your recruiting efforts to foster the current members. Whatever's happening, you can see onset of ennui.
A solution: Find some outsiders! This is more than just a renewal of your recruiting efforts, although that couldn't hurt; this solution relies on you finding people who will challenge your community. Have a community of Hybrid car owners? Find someone who will come in and write a post about the negative effects of Hybrid manufacturing (I'm not sure if there are any, but bear with me) - this injection of change and counterpoint will help liven up a community and also, perhaps, educate them.
9. You haven't made the value of the community apparent.
The problem: People are busy. They have tons and tons of choices when it comes to joining online communities. Because of this smorgasbord of choices, if the value of your community isn't readily apparent - they're going to pass.
A solution: Do some competitive research. Map out the pros and cons of pre-existing communities (there aren't any pre-existing communities? Value = apparent) - and try to mitigate the negatives and enhance the positives. The chances are that you aren't inventing the wheel, but you do have the opportunity to replicate or re-invent the wheel, right? The information is out there - so go get it. After you figure out where you can add value, you need to work on a short, concise value proposition. A pitch! Can you fit that pitch into a tweet?
10. You don't know why you have a community.
The problem: You think you know why, and you think the answer is "because I need one." While that may be true, this cannot be why you have a community. Why do you need one? What are you trying to do? What problems are you trying to solve? If you've managed to establish a community, and you still can't answer this question - well, better late than never. So...
A solution: Establish definite goals. At first blush, this may seem to contradict the "let your community evolve" bit mentioned earlier. You can always add or subtract goals, if need be, or you can simply allow the path to achieving a goal to be flexible. There's more than one way to... peel a banana? Alright, not the best imagery - but I chose to avoid going all Winter's Bone on you and use cat or squirrel skins. You'll thank me later, maybe.
To read more about studies related to online communities, including the inspiration for this post - check out The Virtual Community Blog, which has wonderful (though, dense) blog posts about the structure of communities, and the links to a wealth of research.