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No updates yet on their Twitter status account: https://twitter.com/@githubstatus
Edit: 10:21 PDT Error rates are subsiding. (And github.com no longer showing unicorn for me.)
Websites, even massively popular ones, go down from time to time. Unless there is a post-mortem with interesting technical reasons for the outage, there is nothing to be gained from talking about it. If you need further evidence, just read the comments on this thread. It's just a bunch of "me too" posts. Or reposts of information sources that anyone who cares about the outage already knows how to access.
EDIT: "We're investigating a high number of errors." https://twitter.com/githubstatus/status/711965206029725697
Edit: It's back now