If you want to keep your account "secure", login with Facebook, Twitter, or Google. I know that might turn some people off so I included the username login as well.
Future versions will let you set an optional password to "save" the username.
Meh. You could also tie the user to the device or browser and avoid a first time user entering the game with 2k points and the map nearly complete. Give a new user a good experience and maybe they will use your login mechanism and become a repeat user. Otherwise they might just think the game is broken and never return. I wondered why it said I had answered over 40 questions when I only answered 2. Makes for a poor user experience.
Future versions will let you set an optional password to "save" the username.