This is a great strategy for gaming systems, a terrible strategy for accounts used as identity management and password recovery vectors.
Let's say JamesSmith@yahoo.com used this email address long ago as his ebay recovery address, but really doesn't use his @yahoo account any more. I can register JamesSmith@yahoo.com, and use ebay's account recovery option to assign the ebay account a new password for an ebay account I have now stolen.
This scenario isn't possible with an online game account name, as game accounts aren't used to recover bank passwords or other important account passwords.
