Of course, when someone buys an ad on television, there is no telling how many people watch it, either. Any advertising is at risk of being ignored. “Half the money I spend on advertising is wasted,” John Wanamaker, the 19th-century marketing pioneer, famously said. “The trouble is, I don’t know which half.” Which gets to what is different about digital video: If an ad can be described as “unviewable” — for instance, it is running low on a page, in a tiny player — it’s all but certainly in the half of an ad budget that’s being wasted.

Advertisers are beginning to catch on. At a recent industry conference filled with online ad executives on both the buy and sell sides, and hosted in upstate New York by the website MediaPost, one of the best-attended panels was titled “Buyer Beware: Video Ad Fraud Is Growing.” The problem is that dozens of businesses in an assortment of categories are earning huge sums from the status quo.

“Except for the advertisers, no one has a vested interest in spending less money,” said Jeff Semones, president of M80, a direct-marketing company, who was at the conference. “Whether it’s the publishers, the ad platforms, the agencies that manage these activities. Right now, it behooves almost no one to clean up this mess.”

A Dutch Auction for Space

The mess starts with the ecosystem of companies in the online video ad world, which is so complex that it seems designed to baffle. A common refrain among veterans in this field goes something like this: “I’ve been at it for six years, and I still am learning how it all works.”

A flow chart of this business would put advertisers on one side, consumers on the other and in between a series of chutes and ladders with a dozen different players — media-buying desks, demand-side platforms, supply-side platforms, syndicators, data management platforms, encoding and transcoding companies, ad networks, branded content distribution companies, video delivery management companies — the list goes on.

To grasp how this thicket of companies makes the system opaque, consider some Oscar Mayer ads that could recently be found on The Daily Caller, a conservative Washington website, with 11 million unique viewers a month. Some of these Oscar Mayer ads were high up on the page. But many were posted so low that they were near the comments section of individual articles, in small players that rolled automatically when pages loaded.

The seemingly simple question: How did that ad get there?

Alex Treadway, the site’s chief operating officer, said an answer would not be easy.