Earlier quoted context omitted.
Iframe of the affiliate link. eBay sets the required cookies.
Wait, so they just rendered an iframe of a random product on ebay that contained their affiliate information on a bunch of widgets they hosted ... and this lands you in prison? Lets imagine I publish an eBay widget (I don't) to promote products I think people should buy. Lets say the widget just renders products in my sidebar. Lets say thousands of blogs then install this. Would I be then bound for prison? I'm strugg…
Your hypothetical scenario is actually showing products.
According to the article, it seems eBay's gripe was that once the cookie was placed, the transparent .gif on their homepage was never triggered, so these affiliates were not sending traffic to eBay, but randomly waiting for these eBay users to purchase something from eBay.
This method was actually used by several successful affiliate marketers, now considered "industry veterans", in the early 2000s for Amazon.com and other big affiliate marketing programs.
It would eventually get one kicked out of the affiliate program and the violator would not receive any of their commissions, but this is the first I have heard of the FBI federally prosecuting affiliates for cookie stuffing.