It is tempting, when starting KM in your organisation, to set up a Knowledge Management community of practice as a way to demonstrate the value of communities. I suggest this may be a mistake!
Firstly in the early stages of KM, Knowledge Management is not yet a practice area. There is no large group of people in the organisation who have KM as their main role. They may be interested in it, they may be passionate about it, but they are not yet practitioners. Any KM community will therefore be somewhere between a community of interest and an innovation community, and not representative of the business CoPs you wish to establish.
Secondly, even if you are successful with your KM CoP, it doesn't really form a showcase for the rest of the organisation because of the credibility issue. Going to managers in the business and trying to sell KM on the basis of "look at our Knowledge Management community and how well it is working" is a bit like a car salesman trying to sell you a Lexus by saying "I drive a Lexus myself - it's great". You would not believe him, and the manager in the business would not believe you. She wants to see other business managers who have gained benefit from KM, not KM enthusiasts endorsing their own product.
Thirdly a KM community will not, in the early days, demonstrate business value. KM is not yet a core competence, there are no KM metrics, there is no baseline of KM performance, so you cannot show the savings that will convince the sceptic. This is will be difficult even when KM is mature, as KM is a support function rather than a frontline function (we support the sales staff, the engineers, the knowledge workers), so our metrics are one step away from the hard business metrics.
If you wish to set up a showcase community of practice pilot, then choose a frontline function, an established area of practice, where you can show business benefit. Then later on you can set up the KM community of practice once KM has become a practice area. Prior to that point you may need to establish a network of KM champions, for example, but do not treat this as one of your public pilots, and recognise that the nature of this network will change as soon as KM roles are established in the organisation.
KM will not become a practice area until KM is embedded, which is when the KM CoP will really take off.