Everyone in the ad industry can see what the problem with online viewability is.
Not enough of the leading players, particularly media owners, can agree on joint standards.
The problem has been persisted for years and progress has been slow.
How much of an ad needs to be in view for an advertiser to be charged? 100% of the image? 75%? 50%?
How long should the ad be viewed if it’s a static image or a video? One second, three seconds, ten seconds, or the entire ad?
Is auto-play, in-stream video inferior to an active decision to play an ad?
Viewability matters because it is connected to so many other issues including brand safety, independent measurement, transparency in media pricing, and fraudulent bot traffic.
And when the leading players can’t agree on joint standards or a joint industry currency, it’s no wonder that brands and agencies are questioning where they spend their money, especially in video.
Agencies showed their frustration last week when their trade body, the IPA, wrote an open letter to the UK heads of Google and Facebook, complaining they need to show more responsibility and move faster as the two biggest online media owners to tackle viewability, brand safety and measurement.
A major point of contention for the IPA is the reluctance of Google's YouTube and Facebook to sign up to the industry-wide Digital Trading Standards Group's joint principles, which have been drawn up by Jicwebs, the joint industry currency for online advertising. DTSG is backed by the IPA and other trade bodies including ISBA and the IAB.
Google, on behalf of YouTube, and Facebook insist they want a good relationship with agencies and are willing to consider signing up the DTSG principles, which require independent, third-party measurement.
It is clear that the IPA has got fed up of waiting, even if its decision to go public in the dog days of August seems curious timing.
Most UK executives at Google and Facebook appear to have good intentions but they are almost certainly constrained by the fact that any important decision is made in Silicon Valley and the tech giants are fond of keeping their measurement data for themselves.
It's not as if traditional media owners are perfect. Most national newspaper publishers have not chosen to sign up to Jicwebs' DTSG principles, despite some promising they would.
Advertisers and agencies have some power to change the discussion, particularly when they are the biggest operators in the market.
Procter & Gamble, the world’s biggest advertiser, slashed its global digital ad spend by $140m (£109m) in the April-to-June quarter, with no immediate hit to sales, because it said too many of ads were being viewed by bots.
Leaving aside P&G’s motivations at a time when it needs to boost profits, its change of strategy has laid down an important marker.
Group M, the world’s biggest media buyer, is also trying to do its bit as a market leader, announcing new global standards for video viewability.
It already considers an ad viewable when 100% of the pixels in a display ad are in view and 100% of the video must be viewable for 50% of its duration. However, it has relaxed its rules around video on social and mobile because of the rise of auto-play and viewing without sound.
All this matters because online video players will never enjoy the same level of trust as broadcast TV unless they operate to the same standards.
Online needs a joint industry currency that everyone will support.
Editor's note: This column was updated to include more detail on Group M's viewability standards