Brian Chan, one of the Liferay founders is presenting at Jax 08 about how to use Liferay for scalability:
"How do I scale massively the way Facebook and MySpace do? Both Facebook and MySpace are written in scripting languages that have inherent benefits that traditional Java technology-based portals lack. The session shows how to run your own Portal without using HTTP sessions, so that a deployer can scale the same way Facebook scales with PHP and MySpace scales with ColdFusion."
Of course, Mediblog.com will be outrageously successful and all our problems will be related to scaling up to meet the demand. Well possibly. Seriously though, it would be interesting to hear this talk as I have some concerns about Java scalability vs performance following uncertain experiences with SAP Web Application Servers, sadly time & money are against a trip to Germany to hear it :(