Generally, conferences don't really understand this, although some accomplish it anyway. PC Forum is an experience, from checking in to mixing to, yes, the formal sessions, although those formal sessions (like at any conference) are usually the least interesting thing.
Our discussions of OOPSLA have focused much on the tangibles and infrastructure, the "visible matter" of the conference. But the dark matter is more massive and more important, and other than talking about the community aspect of OOPSLA -- a vitally important aspect, true -- I think we've ignored this.
Such a unique experience can also help to bind speakers. JAOO has just recently initiated a speakers' alumni meeting. I appreciate this idea as it allows for networking between different "generations" of speakers.
The same idea could work for attendees as well. Belonging to a community of attendees can be part of the overall unique experience, and mentally bind people to OOPSLA.
Smaller conferences sometimes get such a feeling of community without much administration effort, but OOPSLA does not want to be small.
- kmq