Same with me. I called AT&T just now and they said that other users are reporting that they see "Dan" in the upper-left hand corner of their iPhones as well... and it all happened at the same time! @Dbo82 I think you may be right, it could possibly be a hack into the AT&T network.
I'm going to power down, pull the SIM card out and power back up before reinstalling the SIM to see if that makes a difference. I am in PA in case anyone else is experiencing this in the region-maybe locations can help AT&T or Apple sort this out faster.