Backing up data then storing it to be infrequently read and handing a major spike of traffic are two very different things.

HN has been bringing down a few sites that were unprepared. True, it's possible to harden your page for unexpected traffic spikes, but that's always work and maybe you just decide it's not worth the effort and invest the time elsewhere. (whether that's a good decision is up for debate)

You're thinking scalability. What they do is reliability in archives, and "team work" (it's in the name) for retrieval. Cheers

HN can direct more traffic than you think, and it can do so very quickly. AT's backing up skills are fine, and if you've managed to be on HN for nearly 5 years without hearing about them then that does not make me too confident about your reading skills :)