I doubt it, with so many accounts there I guess it would be a nightmare sorting out the multiples from the genuine ones. There are other ways of protecting against duplicate accounts though.
You can think it in this way>>> In a family there are 5 members, each have his/her you tube account. You tube cannot afford 2 ban the a/c, unless something very "fishy"/"suspicious" happens.
they do not care about multiple accounts. They really care about you clicking on your own ad if you have logged into your account with the same IP that is doing the clicking. They take that pretty seriously.