The OCC concept is interesting: every week, at the same time, in the same place, a meeting takes place. The focus of OCC is on Internet entrepreneurship, but one could re-use the same structure for any other topic ... something I've missed with other offline social networks - I need to find out where it is this month, which day, what time. If I miss it I wait another month before the next opportunity. OCC is every week - I don't need to obssessively attend each and every meeting.
On top of that, it's completely informal. There's no speaker, no agenda. Just tables, chairs, people and drink. OCC seems to belong nicely with Open Space and similar unconference approaches to building communities.