A friend last night showed me his iPhone and was laughing at how AT&T and Apple were doing this, and he admits his phone isn't 4g but it says it is. Here's an article I found
AT&T 'working with Apple' to show 4G indicator in iPhone4S status bar (update: confirmed) | The Verge
AT&T 'working with Apple' to show 4G indicator in iPhone4S status bar (update: confirmed) | The Verge