Is there a practical limit for gh-pages though? I think you get flagged for manual review if you're high traffic; but as long as you're serving content I don't know of anyone being taken down (and I have heard about some great lengths gone to to keep things up).

And you can put a CDN in front of gh-pages too! I have done that with cloudflare a couple of times for relatives that want to run a static site and super low cost.