YouTube IP Ban - What Does It Take?

I know someone who was IP banned from YouTube, and ever since that occurred, I've been what I think of as overly cautious about multiple accounts on YouTube, and it has been limiting my success as a whole on YouTube.

So what I'm asking is this: Does anybody know what it takes to get IP banned from YouTube? What can't you do?

Bump in the form of a question:

Would I be safe buying 250 accounts and selling ratings with them?

It means that you can't register at youtube with that IP address.
I recommend you to change it. It depends on your internet type (cable,adsl etc.) and your internet provider (is your IP dynamic or static).

Sometimes only your ISP can change it (if they "want").

I recommend you to call them and ask for this.

I wasn't banned, I was just wondering what they will ban you for.