If the seams do not denote a replaceable battery, what are the chances that they could delineate a section of the phone which you could interact with in some way (such as touch response)? The seams mark off the section of the phone that the majority of people will rest their fingers on whilst talking. I know that there doesn't seem to be anything in the internals that suggests this, but perhaps in a finalised version? I'm just daydreaming at my desk here... it's fun.