Don't get me wrong, I don't think SMS on a truly large scale is trivial. I do, however, think SMS messaging is fundamentally different to what Twitter is doing.

Don't get me wrong, I don't think SMS on a truly large scale is trivial. I do, however, think SMS messaging is fundamentally different to what Twitter is doing. The former is unicast: I send you a message. It needs to be stored somewhere (your SMS inbox). Twitter is multicast: I send a message, everyone who subscribe to me needs to get that message. Now, misunderstand me correctly; I don't think this is anything new. My former boss built tools (over 20 years ago) that ran such systems as the NYSE, Swiss Air-traffic control, etc that did fault-tolerant multicast. And the uptime there was somewhat better than Twitter. What led me to post the original comment was this: They are not solving the same problem, but if they were their architecture would be just as flawed as Twitter's.