Sure, there are any number of phones with dual SIM card slots, most of them built for Asian markets, but the iPhone 4 is about the furthest thing from dual SIM: in fact, it doesn't even have one Big Person SIM to call its own. Luckily, USBFever has a hacktastic solution to this problem (a followup to their iPhone 3G version), with a new $30 case that can host dual full size SIM cards on the back of an iPhone 4 (entombed in some classy clear plastic, naturally), while running an adapter to the iPhone 4's micro SIM slot. You can then switch between the two SIMs from the iP
