Yea, we were playing halo pc in my enginering class to demonstrate networking (best class ever) the "keygen" gave keys that weren't valid on lan, and keys that were identical. Even if it was a gen, if bungie used it enough eventually it would spit out duplicates.
you are gulliable the "gens" only had a list of about 25 keys. Bungie will simply use the gen numerous times untill they stop getting unique keys and they will blacklist them.
yes typical, he needed step by step instruction, complained about a free game, had a lisp, and was to retarded to realize his mac had a crappy video card.