Quick note on using full names - we originally were using first name + last initial, but we had a number of e-mails from individuals thinking that they'd won. In the interest of not being a heart breaker, we've gone to using full names.
Even then I had to send a sad "you didn't win" e-mail to someone with the same first & last name of a winner.
I like the idea of using an optional nickname or something similar, I'll feed that back to the team, thanks!