One could say that the Apartments is a place where these groups could have a home. :)
Also, the 2010 Membership Survey showed the following:
13 people used the Guilds on a daily basis
46 on a weekly basis
31 on a monthly basis
44 on a rarely basis
Out of an active membership of 500, having...
http://library.tarvalon.net/index.php?title=Guilds
What you describe as a sense of belonging could be the "community building" aspect. This is still present in the Discussion forums.
Having member created subgroups for that sense of belonging when not part of an Ajah or Company is a common...