| There was a dozen plus last I worked in the field. There are scores of horror stories related to ad fraud. In particular: - PPV ads that get stacked. That, several ads laid out on top of each other so that only one (if any at all) is visible. - PPV ads that get served to bots. Sometimes purposely so, other times as a result of phantom users who replay sessions to build fake profiles for PPC purposes. - Ad injection that replace legit ads or include new ones via browser toolbars or compromised devices. - PPC fraud, of course, including some combined with all of the above. - PPA fraud through cookie stuffing, meaning flooding browsers with cookies to make it look like the traffic originate from where it doesn't. - PPA fraud through ad injection. Nothing converts better than a popover served via ad injection for the very site you're shopping on. I'm sure I'm forgetting quite a few, but at a high level those are the main ones to be aware of. As an advertiser you generally cannot rely on the stats you're provided with. |