We are actually doing this kind of thing -- with a lounge area. We are having "ask the community expert" where we are taking our most active users (who also happen to be SMEs) and offering 15 minute sessions for other members to sign up and have their resumes reviewed, ask questions about projects they are working on, get feedback etc.
We're sending hand-written invitations to our next tier of most active users and asking them to stop by for a little happy hour, hoping that they'll help jump in and stir up conversation with other members who come by the area but don't have scheduled appts. We aren't asking them to do this, just want to see if it happens.
For those who aren't active at all, we're hoping they'll get drawn in (we're having a few other things to help with that) and we'll have group sessions on how to make the most out of the community.