Yes, it's deeply worrying. And the source is Less Wrong of all places, an author with what seems like a solid track record and lots of karma. Really makes you wonder where we're heading.
Ok, do you think 1000 is way too low, or way too high?
E.g., How many life-threatening emergencies do you think happen per hour across the world? How much extra time did it take to reach the average injured person over the outage period? How was the base rate of iatrogenic death affected by losing access to all electronic records for inpatients?
If you come up with a fermi estimate more than two orders of magnitude lower than 1,000, I will be suspicious of your assumptions.