It's exciting to be on the cutting edge of a concept, and mithril is now doing just that. Mining on the Ethereum blockchain while doing something you enjoy seems like a lot of fun.
Mithril is developing a vision for how social media should operate on the blockchain, and it's only a matter of time until huge names like Facebook go on board.
The notion of social mining is brilliant since it rewards people for using the site.
The notion of putting it on the Ethereum blockchain is a terrible one since it might cause congestion if there are a lot of transactions going on at the same time. I recommend that they construct their own blockchain, similar to the Steemit blockchain, which is a stand-alone blockchain.