OK, let's say some dude gets bored one day. He takes your adsense code from your site's source code, and puts it onto his porn site. Your only option is to contact him, or start using the Adsense Whitelist (This would be annoying because for people who own a proxy network or lots of sites, constantly adding new domains is annoying). So you try contacting him, but he doesn't respond. Google later finds out, and bans you for putting your code on a page that violates TOS. What do you do? (This isn't actually happening to me, I'm just wondering what you would do in this scenario)
They have a feature that allows you to avoid this problem: "Allowed Sites" (or something to that extent)
This scenario is unlikely to happen, but if it really happen, it's too bad coz Google has the final word on banning accounts.
Now google like to ban a domain (site), not to ban an account. If google ban a domain, and email you, simply reply that site is not yours If google ban your account, mail them to explain that that is not yours, and maybe you can get unbanned