Real Time Cloud?

Can something like Twitter, the popular microblogging service, be truly real time - where all Tweets are distributed to web, cell phone and other followers in real time or nearer real time - and also handle spikes (like at a big event) as well as higher order business and filtering logic? Twitter is known to have stability problems that they refreshingly admit to. It is certainly a messaging system so a real time message-driven or event-driven architecture as part of the answer as opposed to its content management-oriented approach seems to make sense.

But what does this mean? And will it really help it scale while still providing the user experience it needs. Not sure what the " complexity and unpredictability" they talk about is, maybe there aren't off the shelf technologies but maybe the answer is in the cloud - cloud computing - particularly for handling spikes, flashes and even denials of service.