When talking about Google, you have to be careful with wording. There's a difference between being outright banned, being penalized, and being told to leave the program.
There's no rules against doing arbitrage with AdWords. Google doesn't like it, but they permit it, unless they feel your ads are misleading, or in some way leading to a poor user experience. They reserve the right to decide what's a poor user experience. In these cases, they may tell you your business model is a bad fit for theirs. There's no accusation of wrong-doing - they are just choosing not to do business with you.
If you break TOS in some fashion, then you will be banned. That means you are out, permanently, with little or no possibility of parole. Your ads are shut down, and you can't join back in with another account or credit card - at least, if they find out, they will keep shutting you down. There is almost no appeal from this - I was actually mistakenly banned in 2002 (which is another story) and was only just this year allowed to take out an account under my own name, after I posted the entire story on WebmasterWorld and someone from Google read it, realized the absolute idiocy of it, and got it reversed. That was FIVE YEARS.
Now, what most often happens with arbitrage is that you may be penalized. That means your bids suddenly go from what you want to pay up to some unreal amount, like $5.00 or $10.00. That means your Quality Score took a dump, and Google is telling you to either improve the user experience (comprising your ads, your landing page, and maybe even your business model) or they will continue to price you out of the market. That's where adding unique content, writing really good ads, and grouping your keywords in an intelligent fashion can really help you.
It's not necessarily easy to do arbitrage with AdWords sending to a parked page. But it can be done. I've done it with thin developed pages, but only just started experimenting with sending traffic to Parked.com pages lately, and I've been spending around 60 cents in ads to bring $17-$20 clicks. That would seem like an astounding success, but I am not at all sure it will last once Google calculates the Quality Score. So I'm not going to expand it out yet until I find out if I get hit with a poor Quality Score first. That can happen at any time, but generally it happens within 3 days to three weeks after you start a new campaign.