Usernames

I added the ability for hackers to log in with a username, and changed the ticket views to display usernames instead of e-mail addresses. This is probably better for privacy, but would break the way the site looks right now, since existing hackers don't have usernames. So, I haven't pushed it to Heroku yet. Do you think there should be a fallback to display e-mail addresses if a hacker doesn't have a username?