How are you banned forever? Can't you just buy another computer, get another connection to the internet, and get around the ban? Or do they ban by credit card?

How are you banned forever? Can't you just buy another computer, get another connection to the internet, and get around the ban? Or do they ban by credit card? Or does that just mean the particular domain name is banned? I've got around many a ban by just switching out my computer and getting a new internet connection. Just curious.