Couple of years ago, some manufacturers tried to offer flash memory keys using the FireWire interface instead of USB, but the relative high cost of NAND and the cheap price of USB killed their marketing success.
Today, as flash memory is now cheaper and storage capacity have dramatically increased, some manufactures could re-enter this market. As reported by
59hardware, OCZ presented FireWire-based flash memory keys during the CeBIT:

OCZ would offer FireWire 400 and 800 flash memory keys with either 16 or 32GB storage capacity.
If the price is not ridiculously more expensive than the USB version, it might well be a strong success among Mac users, as FireWire 400 remains faster than USB2 when it comes to get access to data storage units.