Apple vs. Nokia, RIM and Motorola On Nano-SIM Standard
angry tapir writes "Next week, two proposals for a new, smaller SIM card, dubbed nano-SIM — one backed by Apple and the other by Nokia, Research In Motion and Motorola Mobility — will go head-to-head as ETSI (the European Telecommunications Standards Institute) decides which card future smartphones and tablets will use. Measuring approximately 12 millimeters by 9 millimeters, the new SIM will be about 30 percent smaller than the micro-SIM. The thickness of the cards has been reduced by about 15 percent, according to Giesecke & Devrient. The nano-SIM is also approximately 60 percent smaller than traditional-size SIM cards."
After a certain point, you may as well forget the SIM and just build it into the device.
Items that are meant to be removeable and transferable need to be large enough for a consumer to manipulate with their fingers.