I believe that the key ingredient required in a great community manager is passion. A passion that manifests itself in many forms.
A great community manager has a passion for people, technology, and problem solving. A great community manager has a rare blend of right-brain and left-skills - they know when to be analytical and when to be intuitive, when to make a decision based on what the data says, but also can read in-between the data to see what their community really wants.
The job of being a community manager requires a very diverse skill set - I'm not sure if the question is "what specific skills do I look for when hiring/developing a community manager" or "what kind of person makes for a great community manager"?
When I'm hiring CM's, I look first and foremost at whether the person is innately social or not. Are they the kind of person who remembers birthdays of co-workers? Do they bring in treats to the office for no special reason? Are they the kind of person who notices and comments when someone gets a new bicycle, haircut or attained some personal achievement? Are they kind of person who LOVES organizing events, parties or special occasions for others?
These are intangibles, but traits I look for in a great community manager - these are attributes that tell me that this person cares about people, and above all else, a community is a collection of people, and people need attention.
We all love it when someone makes us feel special for no apparent reason, and a great community manager will do that.
Beyond that, the actual duties of a community manager can vary so greatly that it makes it difficult to say what other attributes I look for. Certainly, an ability to plan and execute on a plan. I also look for skills in presenting and developing strategy.
Since a community is a collection of people, what do you want these people to do? Or what do they WANT to do? Healthy communities feel like they have a purpose, and the community manager is the person who helps shape that purpose, so they need to understand the desires of the members AND the business objectives of the company that is funding the community.
So a great community manager needs to have a keen grasp on business strategies and objectives, but not get so caught up in 'business' that they forget that the community members are there for their own *personal* reasons, and the business objectives are only met if members feel personally satisfied.
It's not easy to find someone who understands and can fulfill both personal and business needs at the same time - but that's what makes a great CM, imo.
I hope this response helps - if you're looking for more specific *skills* that a great CM should have, that's a different discussion than what I've responded with here, which is "what are the *traits* of a great CM?"
A discussion that I'm happy to have if you wish to continue the conversation. It's a very provocative question - thanks for asking it. :-)