I got the $100 bonus in only my 2nd month writing with about 7 articles under my belt and none of them seem to very viral. But, I've seen Medium following along into the digital stock photography model where they reward people who make more with more money. People that upload more stories over time rise to the top of the algorithms and get distributed more. Because people don't really want to read stuff from new members because it's a crapshoot. Those with more followers will always end up making more money for everyone (Medium and the writers).