We see this with twitter, message boards, and (heck) anywhere people gather. I want to be in the cool club, but no one after me because "those people" don't get it or are lame. Who is "worth" following? Same feelings, different groups.
If other people steal the emblems of my identity (by liking the same band I like, or going to the same conference I do), it's as if they're stealing my soul. Worst case scenario, I might have to admit that I'm not that different from the average guy. That's a bitter pill for a lot of us, especially those who were raised with or otherwise acquired the idea that we're exceptional or superior.
An interesting irony about this is that the ego dynamic underlying it all is so primitive and so identical.
In small, cohesive groups communication IS simultaneously MORE efficient and MORE intimate.
As the group size grows, the differing mixtures of shared properties amongst its participants grows. There are more total possible channels for signal-based bonding, but also more noise. With choice comes confusion, ambivalence, and even rejection.
In the extreme case, the original cohesive set of properties in the "core culture" can be bifurcated or disappear altogether.
It's no different than what happened on the original Fidonet, The Well, or the infamous AOL-invasion of the academic Internet.
SXSW has simply gotten too big for the original cultural center to hold.