Perhaps an astrophysicist will one day explain why communities like Reddit tend to implode.
Once the "pressure" of those in the core, which are the ones doing most of the work to keep people in line and promote healthy community behavior, start to fizzle out and aren't replaced, the core will implode and the whole thing will go supernova.
Smaller communities, like smaller stars, seem to have much longer lifespans.
The good news is when a site like Digg or Reddit goes supernova it spreads a lot of well-intentioned people around the greater internet to create their own new communities and start the process all over again.
