What is the capacity per block for registrations using Blockstack?

Initial registrations can be done at an order of hundreds per block and once an identity is registered you can do “unlimited” updates to the data because that is off-chain. We’re also working on a more scalable solution where a very large number of identities can be registered but that’s not live yet and is in the pipeline as a rough benchmark. in summer 2015, Blockstack did 30,000+ identity registrations in a matter of few days live on the blockchain and Blockstack was actually throttling its servers and not taking up more than 100-200 transactions per block. It could’ve easily taken up more transactions without impacting the network.