It doesn't make sense why they would. They are hurting their own cash cow too otherwise.
Not if they think they can get away with it. For the record, there is already very compelling evidence ghash.io was abused to pull off double spend attacks:
https://bitcointalk.org/index.php?topic=327767.0Now you may not have sympathy for the victim here, being a gambling site accepting zero confirmation transactions, but if this is not reason enough for you to switch pools, honestly you deserve what it could lead to.