Issues are disposable data, it has an expiration date. Once you closed an issue, there's little value in it. Most of the valuable data ends up in the Wiki (or in code), and Wikis are actually Git repositories. You can't make it easier to backup.

Wanna try it? Take any repository, for example Hubot: https://github.com/github/hubot. Now go ahead and run:

git clone https://github.com/github/hubot.wiki.git

Issues are an important part of a product/library that is evolving. If you loose an edge case bug, you could take months to face it again.

You could also use the GitHub Issue API http://developer.github.com/v3/issues/ to backup the issue data

I didn't know the ".wiki" notation for downloading it. Thanks!

Every repo can be cloned down as normal. ~~I'm not certain about the issue tracking.~~

Edit: according to a quick Google search issues can be exported in JSON format.