If you tell Google about your case and they deem it acceptable (ie. they banned you for fraud clicks but you prove to them that they were legit, or something like that) they will unban you. It's been done before.
You will get warned for pretty much everything except the dreaded "invalid clicks" from my experience. But if you were banned justly, you will never be unbanned. That's why it's called a "ban", and not a "suspension".