The idea is to connect a little big larger groups that you have in mind, people that have something in common. Something like "single dog owners in Finland", "single people in Finland who like to hike", who have existing communities, for exmplae in Facebook. Such groups seem to have 1-10K members. I think the sweet spot is communities with so many members that simple Facebook introduction threads are no longer feasible, but people still have something in common that they strongly identify with.
The group administrator can decide whether the group is public, i.e. visible in listings or not. I have done a small pilot, and that was invite only, with the link in the Facebook group.
If anybody is interested in working with this, help would be very welcome. The platform is based on python/django with a little bit of Javascript sprinkled on top.
While there are some small coding things needed to do to scale it up, the biggest help would be to work with somebody who would be interested in promoting the site to potential beta users (i.e. groups), for example the communities they are personally involved in.