TL;DR: currently Onename is the most “developed” solution for ID info backed by the Blockchain.
The idea of the Blockchain as a ledger for identities was born years ago and the first fork (copy) of Bitcoin was Namecoin – the blockchain tailor-made for names, titles, domains, identification data, copyright and similar info. The blockchain of Namecoin is merge-mined with Bitcoin’s for security (it “piggybacks” on the larger network), and many different services already use Namecoin’s blockchain to store these certain types of data.
OneName offers a service where you can register a name on Namecoin’s blockchain. Once confirmed you can tie your social media accounts (and much more) to that name – and have OneName “issue” a sort of passcard. This card can the be used as a form of “identification” online, according to Onename. However, they’ve pivoted a couple of times, probably because there is no money in providing this sort of ID online right now. And no one recognizes a “blockchain ID” in any way similar to the way government-issued ID’s are.
UPDATE Oct 1, 2015: Onename has switched to the Bitcoin blockchain to take advantage of its superior security.
The difference compared to other similar services (not using a blockchain) is that the info tied to the passcard can easily be cryptographically verified, and only the key-holder (hopefully you) can change that info.
Bitnation offers another solution to the ID “problem”, creating a virtual “country” online, where you can register your name, marriage, kids’ births, contact info and anything else you’d expect in a “nation state” using Bitcoin technology – tied to a reputation ranking system.
Bitnation is a work-in-progress but there’s already been blockchain confirmations of events such as marriages and births “in” Bitnation. However, you need to factor in that there is no more land available to base a “nation” or a “country” on, or whatever you call your network. Until legislation allows a “virtual nation” (if ever) Bitnation and ID solutions of that kind is a mere geek dream.
BitID is another work-in-progress. With BitID a user will be able to sign in to a web service using his/her mobile Bitcoin wallet’s camera, by just pointing it towards the screen.
The Proof-of-individuality project aims to solve the problem of scammers using multiple identities within a system. The idea is to use real-time video hangouts (multi-member video chats) coupled with Blockchain anchoring (timestamping of data), adding extra metadata (like your GPS location). By connecting to 5 randomly selected other users and chatting with them live for ten minutes, showing your face, your voice and your location those 5 individuals can “confirm” your individuality. If you do that regularly (let’s say once a month) and make those “confirmation hangouts” into a chain, a system like this could provide an ID of sorts (but not the kind you get from a government).
In any case any “proof-of-id” is sort of a contradiction in terms and any such system can (probably) be spoofed by someone with the proper resources (think computer-generated graphics and voice emulation, or millions of fake accounts sybil-attacking the system, it’s just a question of time). Better to think about these services as just another indication of ID, individuality etc. The whole idea contradicts the laws of physics, even if you meet a person in real life you can not be sure who it is unless you can sample his/her DNA live on the spot. Even then it could be contested. You still need to trust the “authority” issuing the ID.