Why then are the rules for measuring an apparently highly measurable medium such as the World Wide Web so open to interpretation?
Cookie technology is still the bedrock of measuring performance for the vast majority of online advertisers.
The consumer lands on a website, receives a cookie - a tracking device - from ads on the page (regardless of whether they actually see or click on the ads) and visits the advertiser's website at some point in the future. The cookie is then verified and the conclusion is generally drawn that the ad drove the visit/sale.
You are labelled as a viewer of the ad whether you like it (or saw it) or not. And it doesn't stop there. That cookie can be set to sit on your computer for days, weeks and months, waiting for you to visit the relevant website so it can shout: "That was me, I made them visit." The advertiser or media agency decides the length of that window and it can be as long as 90 days.
The industry has begun to self-regulate, based on the common-sense thinking that somebody who was exposed to (but didn't click on) an ad three months ago probably wasn't influenced into a recent purchase. But for online to compete rigorously with other direct response media, real comparability is essential.
This is because other direct response media tend to undercount viewers after the initial short-term response, rather than overcount them. So while a website will overcount me, a newspaper insert that I act on a week after publication is likely to undercount me.
This means that when the cost-per-sale of the media booking is calculated, online initially looks better value than it actually is, compared to other media, and better than more detailed accountability will reveal in due course.
When genuinely media-neutral plans are written, this means less money being assigned to online direct response than online analysis alone suggests.
When times are hard, media scrutiny and genuine value for advertisers become even more important than in boom times.
We need to get to a point where media investment in directly accountable advertising is based on metrics that add up.
Here's the true headline: there's only one cake and for businesses to thrive in the long-term, it needs to be shared out on a fair and factual basis.
Sue Unerman is chief strategy officer at MediaCom, firstname.lastname@example.org