Having explored Ning a bit more, I think it would be a better forum for PD conversations, and could provide some solutions to the time demands placed on educators engaged in collaborative apprenticeship (Glazer & Page, 2006). While I still think face-to-face would be best, it isn't always possible: here we all are learning at a distance! Social networks built on the Ning platform do seem to encourage more of a conversation than what I've seen on wikis and bulletin boards. In fact, I wonder if it might be more conducive to conversations in courses like this than the vista discussion forum? It is certainly more visual and easier to track than clicking on messages and following 'threads.' I always seem to get lost in the formality of that system. There could be security and privacy issues though, although Ning seems to have taken great care to address those concerns.
I'll be watching this web2.0 technology with interest to see if it is adopted by more professionals as a way to engage in long distance learning conversations.