> It seems like most instragram users have over 100 followers[1], if they're all active and connected that means a sizable chunk of likes (or whatever else you can do) when you post something.

Bad assumption, given the 90:9:1 rule (99% lurk while 1% participate)

https://en.wikipedia.org/wiki/1%25_rule_(Internet_culture)

1% does mean a lot when you have millions of followers, though.