In order to participate in the Outlook Contest, you have to choose a username and a password. Your username, password, and the coordinates that you use to define an outlook polygon are the only data exchanged between your machine and the server.
While your password will be stored in the database in an encrypted form, nevertheless, this is not a high-security site, and you shouldn't use a password that you also use for secure online transactions. (It would take a wire sniffer at your ISP, or at the web host, to get the unencrypted password out of the log-in post-back, but this can be done, and the administrator doesn't want to be blamed if somebody does it to you.) The username/password thing was implemented just to keep outlooks from getting vandalized. It was not intended to guarantee high-security. Only sites using the HTTPS protocol can guarantee that a password cannot be intercepted by a wire sniffer.
Also, if you check the "save" box (above the "Register" or "Log In" button) and your browser is set to accept cookies, your username and password will be stored in a cookie so you don't have to re-enter this information every time. (British law requires that I tell you that.)