Good point. Now how to solve this? Rather than saying it will fail, it's better to think how to change things to encourage people to introduce content.
I've come here from being fairly active on Quora, and can see the potential.
While Quora is weak on posts, it looks like Steemit is weak on amassing interest under a topic (Quora does this by centering on questions and answers as well as a rich topic ecosystem).
I think steemit has a lot to learn from Quora in terms of the use algorithms to allow users to curate their experience, and also to mix new and established content in an individual's 'feed'.
But let's be fair. Steemit is in in beta. This is stuff that took Quora years to refine, and it is still refining.
This particular problem can be solved by providing individualized feeds around topics users are interested in, and mixing content from the different channels (new / hot etc) which include the topic areas the user is particularly interested in. And creating a hierarchy of topics - maybe it does this already, but I am only 12 hours in!
All this will come in time.
This is a good model to start from. I had been considering creating something similar myself for a few years, but couldn't get my head around an effective reward system. This seems to be a genius solution to me.
Anyway, looking forwards to getting involved with the community.