Which is kind of a shame -- after Gears of War's "Seriously" achievement (to kill 10,000 enemies) was met, they added a "Seriously 2.0" to the sequel (to kill 100,000 enemies), and that one's been met as well.
So in retrospect, getting 100,000 HKs isn't too hard -- even if you got one every second, it'd really only take you about a day of playtime, which is probably a lot less than a month of realtime, depending on how long you play for and how good a player you are. Maybe in the next achievement update we'll see a really impossible goal for players to work on: 10 million mobs killed? 10,000 instances run? A million players looted in the battlegrounds? There's got to be something in the game that seems impossible for someone crazy out there to work on.