signor_john - 8:40 pm on Dec 7, 2009 (gmt 0)

Also, many AdSense publisher run multiple sites. So it certainly wouldn't be arbitrage to buy traffic for a site that doesn't show AdSense ads.

It wouldn't even be arbitrage to buy traffic for a site that did show AdSense ads if there weren't a discernible intention to flip clicks. I've seen ads for NYTimes.com on my site now and then, but that doesn't mean THE NEW YORK TIMES is a click arbitrageur: It's a legitimate, high-quality "content site" that just happens to run AdSense ads.