Waste of time? Not really. Think of all the projects that rely on it for package management, plugins, etc. Think of all the companies using private Github. Lots of lost productivity.
Not really, you won't deploy live code from github and if you are it's decentralised anyway so you just use your latest private clones and it's exactly the same.
Everyone can keep working happily even using other syncing methods to collaborate.
At worst it messes with the issue queues and integration services.
+1, As stated, this isn't affecting the git repos themselves. :)