BitShares 2.0 accounts have to be registered on the blockchain. Upon registration they are assigned an incrementing identifier (account id).
This comes with many advantages: Besides improved scalability, we have separated the identity from the transaction authorizing signature. In practice, owning an account name is independent from being able to spend its funds. Furthermore, both rights (we call them permissions) can split among an arbitrary complex relation of people (we call them authorities) using weights and a required thresholds.
Thanks to separating authorities from identities, BitShares 2.0 can be much faster in processing delay while having much smaller transaction sizes. Hence, all participants are forced to have a named account on the blockchain. Furthermore, most transactions are tied to an account name and can thus be linked to individuals (this includes transferes, trades, shorts, etc. but not stealthed transactions).
Even though an account is required to be registered properly, we offer tools to improve privacy and anonymity.