Yes, you can do local/personal work, but if GitHub was your only way to share that work with others, or the only place you had your reviews and bug reports, then all of that comes to a halt during the outage. IMX many GitHub users have forgotten (or never knew) how to email or apply a patch so work can go on. They just get totally blocked. As I said in another sub-thread, that's not really GitHub's fault but it's something adopters should consider and (probably) seek to ameliorate.
Yeah, you're right of course, but what's nice is that it's easy to figure the sharing stuff out on demand. That is, using GitHub doesn't do anything to lock you in from a sharing standpoint - it is just as easy to go figure out how to share your code after GitHub goes down as it is to go figure it out beforehand. Certainly from a code review and bug report standpoint it locks you in, but so does pretty much every other code review and bug report tool. I'd love to see a distributed competitor to those offerings take off. Last time I said that somebody pointed me to fossil, and it looks pretty cool for that, but it also comes with an SCM of its own.
