One of the biggest annoyances with OS X is that telnet client, for some retarded reason, has a default setting to auto-login with your current username to the remote system. Finally I’ve discovered a way to disable that! Sure you can type “telnet -K host” which disables the auto-login, but I hate typing that every time. Instead, do this from a shell prompt:
echo “default unset autologin” >> ~/.telnetrc

That’s all! Enjoy.