3 ms·I would be pretty surprised if people weren't already doing this.by boucher 18y agoI would be pretty surprised if people weren't already doing this.paulgb 18y agoIt would be interesting to find out. If any of the big players are doing it, there would be a huge backlash if they got caught for it.boucher 18y agoAd companies already use cookies all over the place to track users, I'm not sure this would be that much bigger of a deal.