At previous conferences I've attended (namely LISA and OSCON), there were a metric assload of Apple users on iChat/Rendezvous. OSCON would frequently have upwards of two dozen folks using the chat service.
Now, OSCON only has about 3 times the attendance of the MySQL Users' Conference does, but has about 6-8 times the Rendezvous proliferation it does. At the moment, there are three other Rendezvous users online, two of which are my friends sitting right near me.
It's a different crowd, and there's nothing wrong with that, but given how much of a presence Apple has here, I guess I expected a proliferation at least somewhat close to the other conferences, per capita, as it were.