Synereo is a cryptocurrency & network that was the first stated social media platform powered by blockchain. It however, was outpaced by Steem/Steemit to the market, and so we haven't seen any use of the platform yet as a service to users.
Now, WildSpark is set to be the platform that will be the first to utilize Synereo AMP as a social media system, allowing an alternative to Steemit, and perhaps something that would work complimentary with Steemit.