Remember that individuals and organisations pay for private repo hosting. Aren't they entitled to an adequate SLA of say 4 9s a year?
As with any purchasing decision you can read the T&Cs when making up your mind and are free to vote with your wallet if you disagree.
Another factoid is that Amazon Web Services (AWS) only offers a 99.95% SLA so where did the 99.99% for GitHub come from?
Why does it matter that AWS is 99.95%? "Cloud" based services like AWS and AppEngine have more relaxed SLAs. GitHub is not a cloud service, its a centralized version control repository. And the 4 9s, well that's just something I've always strived for when providing a service but I do believe we should all hold ourselves to it.
When seen in that light, lots of nonessential services seem equally unimportant.
What's really the impact of Facebook downtime? You have to wait a little longer to "poke" your crush's profile/look at their picture/etc? Give them a break.
Homebrew on OSX is unusable without Github.
Rubygems is kind of unusable without Github.
Several ppensource projects documentation is unavailable without Github.
The other comment was closer to the heart of it: if those projects used Github's paid hosting maybe they'd have a reason to complain.
Part of the beauty of git is that it would be absolutely _trivial_ to have a secondary "backup URL" located somewhere else if Github were down. And git would automatically handle the rest.
You have to wait a little longer to do your push/pull/merge/etc?
Give them a break.