There is a fairly simple test for knowing whether
a community of practice, is likely to be successful; that's the self-identification test - the "I am ..." test.
Membership of a community of practice is driven by passion, and the members are practitioners. Members of a community of practice feel an identification with the community, and an identification with, and loyalty to, other community members. For example, I am a member of several knowledge management communities of practice, because I am a knowledge management professional. At BP, I was a member of the Geologists community of practice, because I was a geologist. Project Management communities are for project managers, Corrosion and Inspection communities are for maintenance inspectors, Copier Repair communities are for people who are copier repair technicians.
I am a knowledge management professional, I am a geologist,I am a copier repair technician - that's the "I am ..." test for a community of practice. A community of practice for topic X will work, if there is a group of people who say "I am an X professional" - if they self-identify with the topic.
Here's a negative example.
A while ago we worked with a company that wanted to introduce a community of practice to cover the topic of annual returns. This was a chore than needed to be done once a year, and people were not very good at it. "We ant you to help us launch this community" they said. "We don't think it will work", we said. "We still want to try it" said the client, and the client is always right, so we launched the community of practice.
It failed. After a brief period of life, it just died away.
That's because none of the members would say "I am an annual returns professional". They were engineering team leaders, they were professionals in their own topic, but annual returns was a chore that they did not identify with. Instead, what they needed was a simple how-to guide - a checklist and an FAQ - that would walk them through the annual chore. Not a community of practice, but a knowledge asset.
So if you are contemplating whether a community of practice is the right solution for your company, remember the "I am ..." test.