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Multi accounting is not the problem. It is not the reason.
the terms and condition looks like need to be revised
multi-accounting is not problem as long as not used to get any 1xbit promotion
in most case multi-accounting disallowed due promotion abuse
it's pretty clear 1xbit officially stated above my post but can't see it on the T&C till now.
"If something is not prohibited, it means that it is allowed."

If in the rules you can not find information about multi-accounting, it only means that it is allowed. For sure website security controls this kind of situations and if someone wants to multiply promotions or will breaks the rules in other way it will end with ban on all accounts.