tvbcof and
passerbyThanks a lot for suggestions!
I like many of them, so I'll discuss them with the rest of the team and we'll start working right away. I like the "internal transaction" suggestion, though I'd rather avoid using either emails or long "bitcoin not-a-bank account numbers" as internal identifiers. I am considering bitcoin address of the vault itself (gox style) though I am open to other suggestions.
Also, I have a few ideas of my own that, to the best of my knowledge, aren't part of any wallet service currently done
Wallet.is team will do our best to amaze
I believe the fact you glossed over TF's issues without any defense shows his comments were dead on. You are going to collect as many coins as you can then disappear.

His issue can be boiled down to "server side storage is not trustworthy".
We at wallet.is don't aim to somehow mend the fundamental trust assymetry of server-side wallets, but we intend to make up for that in valueable features and ease of use. We hope that, by providing a reliable and feature-rich service over a long period of time we shall, eventually, prove ourselves to be "trustworthy enough" for certain use cases.
If I wanted to steal coins, I would have been far better off with something along the lines of pirate scam (entraping people with greed is far easier than entrapping them with a feature rich service - much less code that way

)