Lot of folks comparing instances to email servers, and no matter how often you explain it, that won't make sense to me. BBS? IRC? MMOs, even? Okay, maybe. Email doesn't track for me as a metaphor, though YMMV.
@chuckwendig okay so science fiction conventions.
You can go to a con and still text your friends who are at a different con, and even remote someone in for a panel. But you have access to the hallway track only at the con you're at.