Eli Dourado reports:
Bitcoin also has applications that are not purely payments. As a distributed ledger, it can function as a notary service, providing proof that a given document existed at a particular time and date. Another innovative idea is to use Bitcoin as a bonded identity service. The proposal is to create a system of “Passports,” secure identities verified by the blockchain, backed by “fidelity bonds.” Essentially, you would create a unique identity in the system and then verifiably give a non-trivial sum of bitcoins away to whichever miner randomly processes your transaction. By making it costly to create an identity, this system could be used to ensure that dozens of new accounts are not simply created to engage in fraud, spam, or sock-puppetry. Passports could be portable across different online services, creating a persistent identity that is both pseudonymous and reputable. Reputation rating services could develop to ensure that Passport-holders who misbehave on one service are shunned on other services.
There is more here.