Difference between local and cross-local communities of practice in online tools

I am part of a number of CoPs, most of which are international by essence, such as Pionneers of Change and the Society of Organisational Learning, not to name them.

In a recent conference call organised by PoC and in which Etienne Wenger took part, it struck me that we talked about the need to have at the same time an exchange between practitionners across boundaries (cross-local as I wrote it) where our common passion and interest that drives us together to exchange our ideas and initiatives online, and the need to nurture local communities of that practice, where proximity allows a different kind of interaction, physical and spontanuous.

My point here is that two different set of functionalities are required to assist local and cross local CoPs. Anybody has some insights about that?

Thinking of local communities, tribe.net or meetup.com come to mind. As for cross-local communities, the list is endless.