Some people don't like video games, prefer sports, like skiing... Some people play Settlers and/or Civilization or turn based strategies... They won't be able to react or move quickly in Portal. It's like saying - we will hire you but you need to BUY and DRIVE this motorbike through this hoop of fire... And person don't even have driving license. Not to mention they were busy building that hoop of fire instead of making their product in the first place (but that's for them to decide how they want to run their business). I juts think being a gamer is not requirement. If you can opt out and solve a chess puzzle or a super fast Tetris or whatever - there should be alternatives, just like audio capcha or sites for color blind people