[jcrites]

The way it was explained to me: originally, Amazon didn't want there to be any barriers to someone making a purchase on the website, not even the barrier of having to reset a forgotten password. So the choice was made to allow people to create new accounts with the same email address (such as when attempting to check out; that's when this would likely happen). Each account was distinguished at login by its email + password combination.

It was indeed called "Multiple Accounts, Same Email", though I only heard that term applied to it much later (after the phenomenon of these accounts was identified as a problem that the company needed to resolve). I don't think it was exactly what I'd call a feature, in the sense that I don't think anyone expected users to do it intentionally, so much as it was "We don't want to lose a purchase to someone getting stuck at the login screen".

The Web and its users have evolved significantly since those early days, and resetting a password by email is no longer the barrier it once was. Among other reasons: web users are savvy to the idea of having accounts, which was not true in Amazon's early days; and email is a lot faster and more reliable now.

Allowing multiple accounts to share an email address proved to be a problematic decision later on for a number of reasons. Amazon doesn't allow this any more, at least not from the primary sign-in screen; it gives an "Email address already in use" error.

[hultner]

Microsoft have a similar problem relaterade to them merging a lot of services but not accounts. I have an old Xbox Live account on my Xbox 360 which I can’t reset the password for since the email/username was the same as for my Skype account and my Hotmail/MSN account back in the days. This mess is still causing me tons of problems anytime I try to log in to something Microsoft related.