Metrics matter. Every online publisher and every digital marketer knows this.

In a new article, BusinessWeek’s Sarah Lacy asks the question: is the ‘unique user‘ metric an endangered species?

Before I answer this question, a disclaimer: I’m not a fan of Lacy. Her hyping of Web 2.0 followed by her newfound skepticism as the hype has subsided leads me to one conclusion – she’s a part of the herd, not an observer of it, as a good journalist should be.

Given this, it probably won’t come as any surprise that I find her latest BusinessWeek article, and the question it asks, to be of little real substance.

In it, Lacy lays out how the viral Web 2.0 services she has often fluffed have made the metric of ‘unique users‘ less meaningful. She writes:

“…there’s a fine line between watching metrics as an indicator of content quality and sacrificing content in the name of shamelessly goosing metrics. And some feel Web 2.0 companies are crossing the line, ironically destroying the value of the very gauge they are hoping to use to boost revenue and profit: the unique user. ‘The virality of Web 2.0 has had one very negative side effect: the devaluation of unique users as a metric for selling advertising,’ says Roger McNamee, managing director and co-founder of private equity firm Elevation Partners and an adviser to several new-Web companies. ‘Web 2.0 startups have figured out how to leverage each other’s uniques, which makes all uniques less valuable.'”

The examples she provides to demonstrate this are curious.

Take Twitter. Lacy talks about the various techniques that some use to boost the number of followers they have on the popular microblogging service, but there’s no inherent relationship between the number of followers individual Twitter users have and the total number of unique users Twitter itself has. Obviously, you can boost the number of Twitter followers you have without increasing the number of unique users that are on the service. As such, I’m not quite sure what she’s trying to say.

But putting her flawed examples aside and getting to the question of the value of the unique users metric, I think Lacy is asking the question about a decade too late.

In my experience, this metric has had limited value for some time. While that’s not to say that it is isn’t important, in the more than a decade I’ve been involved in online businesses, I’ve met few others who considered the unique user to be a perfect metric, the end all and be all that Lacy seems to have thought it once was.

My involvement in the business of the internet on a more sophisticated level began in 2001 and even then, various properties that I was involved with were not treated the same. Some, which were content destinations, were always far easier to sell to advertisers and partners than others, such as community destinations. This despite the fact that oftentimes the community destinations had a greater number of unique users.

The reason was obvious even then: advertisers weren’t using metrics as the indicator of content quality, as Lacy naively infers is the case. They were looking at the metrics and put those in context, evaluating the nature of the content driving those metrics. In other words, Lacy has it backwards.

I’ve met a fair number of unsophisticated media buyers over the years but I’ve met few who were completely ignorant to the fact that content and other intangibles need to be evaluated alongside metrics. It doesn’t take a rocket scientist to figure out why a message board, for instance, might have a greater number of unique users and pageviews than a branded content destination but still be ‘worth less‘ than that branded content destination to a media buyer. It’s like comparing apples and oranges. Is a bigger apple better than a smaller orange? Dumb question, obviously, if you’re looking to make orange juice.

While there’s no doubt that metrics are a tricky subject and the efficacy of the metrics that are most commonly used, including unique users, is questionable in many cases, suggesting that the “goosing” of metrics is a new phenomenon that is diminishing their value is dubious. This “goosing” has been going on for some time but rarely is it effective. Lacy points out that widget startup Slide boasts the fifth-largest “reach” on the internet but I think she’d have a hard time finding a sober media buyer who is going to treat Slide the same way he or she would treat a property like Yahoo.

At the end of the day, one need only look at the rates being paid for advertising on different kinds of websites to establish the substantive issues that are worth considering.

Why do popular Web 2.0 services like Facebook, Digg and Slide have trouble selling ads? The answer is simple: the ROI they deliver doesn’t create the type of demand that would enable them to sell more advertising and to sell it at higher rates. It’s that simple.

When Lacy and investors like Roger McNamee refer to metrics like unique users as drivers for ad sales, I think they lack some required experience, perspective and nuance. In reality, I’d argue that metrics are better described as sales filters.

Media buyers may need to find properties that meet certain metrics-based requirements (i.e. anything with less than 1 million unique visitors a month is off-radar) to make the economics of their business work. But metrics alone rarely close deals. What’s the demographic? How is the campaign structured? Where is the ROI? These are far more important questions.

From this perspective, perhaps the question Lacy should be asking is: are publishers who can deliver ROI an endangered species?

In the Web 2.0 world that she has associated herself with, the answer just might be yes. And if that’s the case, there’s not a single alternate metric in the world that can save them.