Well, the internet is only ~20 years old. I'm not strong enough in statistics to actually model this, but if something "this bad" happened once within 20 years,

Well, the internet is only ~20 years old. I'm not strong enough in statistics to actually model this, but if something "this bad" happened once within 20 years, it might be reasonable to expect it would happen again within another 20. It's possible it is a every-hundred-years event, but unlikely. Perhaps even more often in the future, as software complexity continues to grow?