email as username, pros and cons

[eluser]Michael Wales[/eluser]
I like to use the email address as username if it will not be displayed anywhere publicly. If it will be displayed publicly, I always use a username (or still use email but allow the user to set a display name).

As far as people changing/losing their email address - in my personal experience, I am much more likely to have more usernames than email addresses. It's always harder for me to remember what username I registered with, than if it asked for the email address I used.