If everyone has SSH access to a server somewhere, it's easy to just put a git repo there to let everyone keep working.
Obviously, this doesn't trivially scale to many repos/users/etc, which is why Github exists in the first place.
Obviously, this doesn't trivially scale to many repos/users/etc, which is why Github exists in the first place.
However, I'd say one of the biggest practical problems with most of the popular DVCS tools is still that they don't also have a simple, out-of-the-box way to set up a centralised repo. As you say, using Git+SSH works up to a point, but it's still irritating and somewhat time-consuming to set up if you work with a lot of projects that might each have different contributors. Last time I checked, none of the main alternatives was any better.
This seems to be a fundamental weakness in whatever deployment system is used, then. Relying on a single point of failure outside of your organisation's own control for anything critical is always risky, and in this case it seems to be entirely avoidable.