from http://bitcoinist.net/social-networks-decentralization-synereo-case/ :
"Synereo vision is to improve the model already presented by other social networks, but instead of being managed and regulated by a central authority, it uses blockchain technology to ensure a decentralized level of security and privacy fit for the next generation of social networking. Having this as the main approach, Synereo may well be the Facebook killer."
My google must be off. :)
Being a "facebook killer" invention is something many have been striving for, even before the block-chain integration. Gives it kind of a "meh" hype to it, since you hear it a lot.
I think they can co-exist since not many power Facebook users are on Reddit and not many hardcore Redditors are on Facebook.....
Well, yeah, until it gets going, we cannot really know. But its general structure resembles facebook more than reddit. Users have more control over who sees their content. This is pretty identical to the way facebook operates.