If you care about a remote repository, you once contributed to, could be deleted, you could create a clone of this repo and keep it on a safe state, but this wouldn't be better than keeping your fork of the repo in GitHub.
I personally think, that it isn't an issue if someones account got hacked and the repo would be deleted. As GIT is a decentralized repository system, it's quite likely, that the author of the repo has a copy on his own machine. Specially on a system with more than one active contributor. That about deleting a repo by mistake or by hacking someones account.
If the owner of the repo should choose to delete the repository, you are quite lost. But if you've contributed to a project, it's quite likely, that you have it actively in use, don't you? So, your changes are not lost ... maybe the history in GIT will be if you haven't copied that over as well to your system in production.