A lot of startups or smaller companies I've worked with are entirely on the Google stack (gmail, google drive). I imagine there's a scale when that option breaks, but I think it'd be fine until 50-100 employees.
Looks like University of Arizona uses it: https://it.arizona.edu/google-storage which has 50k students: https://en.wikipedia.org/wiki/University_of_Arizona
No personal familiarity with it at that scale, though.