Good question on the "different messages." When the e-mail from God arrives, the number of variables in it (like the number of letters used in a software registration code) should give us an idea of how many universes there are.

That being said, God communicating with the Earth might be a bit easier. You know, write "Yo! God Here!" on the face of the Moon or something.

Or he may decide that cornfields are the way to go, if He just writes a clear message for a change.

Right now, God uses corn and grain fields much the same way as we use notepads while we're on the phone, to doodle odd sketches while He's thinking about something more important.