I remember Facebook being down for me once. I wasn't the only one but it came back up relatively quickly. Being such a big company I'm sure they have systems in place now to kick in if a server fails. That's like Google going down - imagine that!
If Facebook does go down, it probably won't be for long. I imagine a bunch of alarm bells would be going off, with a small army of SysAdnins running around like chickens with their heads cutt off trying to fix it. :lol:
It wouldn't really affect me if facebook does go down (for short term or long term) as I do not use facebook that much except for running a few pages and getting news on a few groups. I haven't posted personally since 2014 i think and I may of shared something on facebook this year.