I'm on the mailing list for Yours, a project with goals that are similar to Steem's. A little earlier, I got this article in my email.
Plaintext URL: https://engineering.yours.network/articles/2016-07-14-why-we-are-sticking-with-bitcoin/
Here is the Steem-relevant part:
By leveraging bitcoin, we can take advantage of the largest blockchain technical ecosystem including open source software, documentation, standards, and APIs, as well as the largest blockchain social ecosystem including companies and experts. A new blockchain either has no ecosystem whatsoever, or, if we copy bitcoin, has an ecosystem only insofar as it overlaps with bitcoin. Building on bitcoin, though not easy, is easier than doing it alone on a new blockchain.
That’s the theory. A new project, Steem, has has taken the very approach we determined wouldn’t work. They have built their own blockchain and customized it to suit the needs of their community. They’ve grown significantly and now have one of the most valued cryptocurrencies measured by market capitalization. And as best we can tell, it’s actually working — content creators are being paid.
Although we are delighted to see blockchain social media a reality, we worry that Steem can’t last. The burden of building not just a community and a technical platform, but also a novel cryptosystem and supporting economy, is extremely high. Security and scaling problems with their blockchain have a smaller team of experts incentivized to solve them, so solutions will come slower. Companies and services such as wallets and exchanges will be fewer in number and less featureful. When they encounter regulatory issues, they will have fewer allies.