The gamblers that fall victim to such act must be blame op, because they have violated the rule of the casino and the punishment for such offense must be serve to them for applied more than one account. When you have more than one account with one casino is a multiple accounts, but some gamblers don't take their time to read the rules and conditions of some casino before they started registering into the casino with multiple accounts.
I don't know some accusations you have witness against the casino before, but I have seen some evidence casino team have displayed as an evidence of multiple accounts gambler has registered in their casino.
Like I said before, some people make this mistake without realizing it. The casinos uses IP address to link those accounts together and without a gambler having that knowledge and they share the same internet connection, their accounts can be linked, another way is that, if you allow your friends that is using same casino with you to log their account on your phone and gamble, it can also contribute to account linking, when you don't understand this things and you do it, it because a problem.