> Besides, if some particular blockchain succeeds as a currency, it will inevitably host a social networking protocol where the whole network's state (e.g. who

> Besides, if some particular blockchain succeeds as a currency, it will inevitably host a social networking protocol where the whole network's state (e.g. who follows whom, who likes what posts etc.) is always available to anyone interested. I find that unlikely. The volume of social media far out classes that of financial networks. They also have competing concerns. A blockchain is only secure because it uses up lots of resources to ensure that the network is secure hence it costs money to use the network. Social networks are useful because they are low friction: very easy to use, any time, freely, as much as you want. Blockchains are like credit card networks in this respect, you (currently) pay 9 cents to have a transaction committed within an hour (or 35 cents for a few minutes), credit card companies offer a similar service in the 20-25 cent range. I don't see anyone paying 20 cents to have a post committed within a few minutes, or even 9 cents to like a post. That just doesn't track. (Let alone the storage space concerns...) However, a federated social media service (think email) is a much more viable alternative. And it already exists. Such systems could easily publish public cryptographic ledgers, the joining of which would provide one with a state of the network at any given time. Again, no need to pull a block chain with proof of work into this, there is no reason we need to worry about that because trust can come from us knowing other people in the social network. As a final aside, publishing the entire social network isn't even a feature most people want. Not really. Why do you think Facebook has privacy controls? No one really wants to post their entire social media profile on the web in some sort of provable immutable way.