Wordpress serves traffic live out of three datacenters. That is the redundant system. And I can say from experience that it's really, really hard to do that.

Wordpress serves traffic live out of three datacenters. That is the redundant system. And I can say from experience that it's really, really hard to do that. Doing so well is probably the reason they've had such a good record for the last four years. An unexpected condition on the network that keeps the datacenters from talking to each other (I'm speculating based on their report) might have cascaded into a wide-scale outage. It's also worth considering how hard it is to cold-start a large site, if the outage had any impact on their MySQL servers or caches. We can't cold-start Wikispaces anymore (nights and weekends included) and we're only doing ~10M unique visitors a month -- WP has something like 300+ million.