There can be two kinds of identities: your actual legal one and ones you should be okay with losing.
People keep devising more and more involved ways to maintain identities other than your legal one, but if you think about it you can still lose any of those ways (your domain name, your private key, etc.) and in the end no one should use them for anything serious.
Identity also needs to be hard to copy (which is the main reason e.g. you would not want to use your a hash of your DNA as an identity -- it would be hard to lose but easy to copy).
People keep devising more and more involved ways to maintain identities other than your legal one, but if you think about it you can still lose any of those ways (your domain name, your private key, etc.) and in the end no one should use them for anything serious.