Ask HN: How likely is sustained national/global outage of a Google core service?

1. Do you believe a google(or >1B user company)could have a core service(or equiv.) like:

Search

Gmail

Docs/Drive/Cloud

[ other core service w/ >500m daily users ]

Could experience a global(or non-trivial subset) failure, sustained for at least 20 full minutes?

2. Why do you believe this?

3. If you answered you believe this to be possible, what do you think the cause would be [ e.g. internal error, maliscious attack, ect.]