500 - the number of employees before your CEO becomes a political figure
1000 - the size of company when you’re at risk of losing accountability
From my own experience and other sources (https://news.ycombinator.com/item?id=35206141) those numbers seem too high. I've seen this happen 2 times in front of my eyes while both companies were in the 100-200 range.
One of them managed to go to the next level and adapt to the new reality the other is still struggling.