I just came accross this post https://steemit.com/steemit/@crowdifywepayyou/the-paralells-between-steemit-and-empire-avenue from 
https://crowdifyclub.com/auth/login who made an excellent point which I have also referred to multiple times.
Empire Kred and Steemit both heavily reward the early joiners and while this is OK financially it is not sustainable when it interrupts the dynamics of the community on an every day interaction level. This is why our forthcoming "influence" score will start again every month and why nearly all your Crowdify points will disappear every month if you have not used them.
I believe that you have to give an even chance to someone who just entered the community a month ago to someone who has been there 3 years. Otherwise they will become easily frustrated and continually running off to join the next "big shiny thing". Nobody likes to feel small.
He said : it is OK financially but not sustainable when it interrupts the dynamics of the community on an every day interaction level
I 100% agree with this. This is why it is so important to seperate influence and investment. It is OK for early adopters to have a lot more money than other users but when it comes to the influence which is the dynamics of the whole system it is not OK, it's not sustainable nor scalable.
Here is how crowdify addressed this issue : This is why our forthcoming "influence" score will start again every month and why nearly all your Crowdify points will disappear every month if you have not used them.
Similarly steemit will need a mechanism to keep everyone on a level playing field. The proposal I made recently addresses this issue. Instead of removing points like crowdify does it will make 'points/steem power' over a certain limit partially usable. The steem power that's over 250 MV or 100 MV will not be able to upvote but only downvote. The limit will also be adjustable to make sure levels are reachable regardless of the price of steem. This is absolutely necessary to attract new users. Like crowdify said 'nobody likes to feel small' . Right now on steemit 99% of users feel small, especially newbies, they have absolutely no hope to climb up the steemit ladder. If you want to know why the userbase is still small look no further.
The only way you are going to improve user retention is by making the steemit game accessible to everyone, you can do all the marketing you want or create a comment pool if people don't understand the rules of the game or don't find the game appealing they won't stay.