This is awesome - a brilliant way of bringing different communities and groups of people together, pioneered by a group of Parisians. It's also exactly what I'd love to see on UPSU.net with Portsmouth's student population (and why stop there? Why not make it all-inclusive?).
(Or maybe the whole social groups thing on t'internet is just a manifestation of us web geeks' collective desire to find non-threatening ways of making new friends? Where's a psychology student when you need one? ;o) ).
/al - bedtime