Why won't my iPhone or iPad case work with this cable? is one of the questions we're being asked a lot lately. A naked iPhone can pretty much fit any sync, charge, or media cable you connect it with at home, at work, or on the go. When you start introducing some types of cases, however, and add in different kinds of cables -- all bets are off.
The USB to Dock cable Apple includes with every iPhone and iPad box is typically razor thin. It just has an incredibly small profile and will generally fit almost any case you throw at it. [Cheap plug: the Apple USB cable with AC adapter is 50% off right now at the iMore Store]