I would think one could just go out and purchase a USB key and copy the info over.
Still haven't a chance to think about it..... however, you'll find "dongles" on many expensive software items. Over time, the cost of these anti-piracy solutions will decrease significantly. A USB key is probably not the best solution. It seems like a smart card would be less expensive and provide better security. In either case, the game companies would need a certain infrastructure in place before they could implement something involving hardware dongles.