Communities and Networks

Question 1: In Gray's article about Communities of Practice, facilitators are needed to keep communities of practice together and strong. Kavanaugh's article focuses on the role of someone who is a bridge, who connects the groups together. Bridges are usually more social. So my question is, it seems as though facilitator and bridge have strong overlap in the Gray article, but with Kavanaugh's focus on the nature of the role, how would you best hold a Community of Practice together if the facilitator was not also a bridge?

Question 2: Communities of Practice work partially because of the overlap of common interest (interest keeps it together). If the social structure of the participants is identified and considered, is a COP with many bridgers able to be more diverse in their thinking (possibly offering more perspectives, thus more learning) than non-bridgers, or is subject matter the essential element, and if the information is to diverse, the COP falls apart?