TUAW's been all over the nano-SIM battle being waged in the hallowed halls of the European Telecommunications Standards Institute (ETSI), pitching Apple against the evil triumvirate of Nokia, Motorola, and RIM. Now, just coincidentally, Apple has received U.S. Patent 8,145,261 for "Ejectable component assemblies in electronic devices," which just happens to be a patent for a SIM card tray.
Since the patent was originally filed in December of 2010, chances are pretty good that this has absolutely nothing to do with the nano-SIM melee. However, the design that was patented looks very similar to the design that has been used in the iPhone all along, and the nano-SIM tray design could be based on this.
If you're up for reading the minutiae contained in the patent document, it is available (complete with drawings) from the U.S. Patent and Trademark Office online.