Ah, I remember him being from UK if I am not mistaken (in my first post I was thinking he is from US, but now I do remember better).
If so, I think you should google for "UK Data Protection Act". It is in multiple sources listed, that you have to remove their personal data, if asked, which also means a user account. But as I am not a native English speaker and don't live in UK, you should probably double check it.