> Due to recent changes, App Engine no longer supports mapping your app to a naked domain. If your domain registrar supports URL redirects, you can redirect from http://yourdomain.com to e.g http://www.yourdomain.com or http://appid.yourdomain.com.

http://code.google.com/appengine/kb/general.html#naked_domai...

http://stackoverflow.com/questions/817809/how-to-use-google-...

http://blog.notdot.net/2009/12/Naked-domains-on-App-Engine

(For non-commercial use this limitation may be more acceptable, but if you are seriously launching a commercial service, you probably want to freely choose your domain.)