Shout out here to NearlyFreeSpeech who do this right. They give you a set of verification actions:<p><pre><code>    You provide a scanned copy of a government-issued photo ID.
    You provide a scanned copy of a statement showing both the most recent deposit and a name and address matching one of your accounts.
    You complete SMS verification. (SMS must be previously configured.)
    You complete 2-factor verification. (2-factor auth must be previously configured.)
    You correctly answer your security question. (Security question and answer must be previously configured, below.)
    You use an ssh key to create a file with a specific name on one of your sites hosted here. (Must be previously configured, won’t work if account is empty.)
    We try and fail to contact you via your currently configured email address. (This one may take a long time.)
</code></pre>
You can then pick how many of these you want to require to get your account back (and which you want to configure), including an option not to help at all in the case you lose your account.