For those of you who don't read Pharyngula but do follow Skeptoid, you might want to know that Brian Dunning has been convicted of defrauding eBay* of millions of dollars. He did it by "cookie stuffing."
Dunning and a colleague developed their own little widgets for websites: one was a "where in the world?" widget where you could see where in the world your visitors were coming from, and the other (Dunning's) was just a page hit counter. Totally harmless-seeming and fun little things to have on your website.
Nestled within that code was a sort of sleeper cookie unrelated to the widget's stated purpose. That cookie would only activate (not really the right term but it'll do) if you browsed to eBay and bought something. It would trick eBay into thinking that you had purchased your item via an affiliate link belonging to Dunning, and they would then send him an appropriate cut of the purchase.
This chafes me because I have definitely visited the Skeptoid website on this computer with this browser and have also bought a handful of things off eBay—shame on me for not regularly clearing out my cookies and such, I guess—so I've probably contributed to his ill-gotten gains by crediting him with a couple sales he has no right to claim. I should say that there is no official word on whether he used that widget or that particular piece of code on his website, but it would be naive to think he didn't.
Not the worst thing a person can do, but still pretty shitty.
*I mean it's eBay and not little old ladies, but still.