no there is basically a big DHT like bittorrent and then there is a block chain for individual user identities and they can store chain updates here so other users of the same application also store parts of that chain. this lets you verify that someone else didn't alter their history after they created it but it doesn't give you any of that data.
the data blocks are content addressed and published if the app wants to do so. they can be verified in history by checking with the DHT of other same-app users to see if any weird forks were created (such as the identity owner creating and signing a new timeline) and you can verify that large blob was in the chain at some point. but you can also choose to not publish blobs, so for example you have to already have a copy of an email to prove it was sent (while everyone else just sees that an email of some content was sent)
the social proof aspect is that you get a random allotment of other users on the same application who become stewards of your records and they can verifiably certify that you are obeying or clowning the protocol as the application is written.
this is basically Ripple but instead of a fixed trust chain the people who certify you are randomly selected and have to form a majority agreement.@ParmuTownley @jwildeboer @duniter