[nicholasreed]

Why email it to me though? If all you need to essentially recreate the private key is this tidbit you've emailed me (plaintext, available to anyone), plus the (potentially compromised) tidbit on your server... What am I missing? Shamir's secret sharing doesn't help me if you already have access to all the pieces (your email account and a hacked server).

[derefr]

I assume, by "they don't have it", they actually mean "they had it when you input it into their sign-up form, kept it just long enough to put it into an email, and then erased it."