It won't help you get new users, but it's a good way to let them know you are having problems and communicate when things will be back up. You can't do that if

It won't help you get new users, but it's a good way to let them know you are having problems and communicate when things will be back up. You can't do that if you host it on your own web server and the server fails (unless of course, all your users are following you on Twitter too!)