It may not be the new kid on the block, but email is, for many companies, one of the most effective and profitable digital marketing channels.

It’s not hard to understand why: an email address, like a physical address or phone number, gives companies a means to connect with a known individual across time and space, making it a compelling medium for relationship-building.

Given this, it shouldn’t come as a surprise that many companies are eager to collect email addresses of customers and potential customers. Most reputable businesses do so through legitimate means, but the perceived value of an email address is often so high that some companies are willing to consider shadier tactics.

How shady?

Recently, Sumit Suman visited a website of a social media marketing firm, uberVU. He browsed a couple of pages and left. He did not purchase anything, nor did he sign up to receive emails. So he was rather baffled when, shortly thereafter, he received an email from uberVU thanking him for his visit. He posted a screenshot of the email to his Google+ page and asked how the company obtained his email address.

The apparent answer was provided by Darren Nix, the founder of a company called 42Floors. On his blog, Nix explained:

I’ve learned that there is a “website intelligence” network that tracks form submissions across their customer network. So, if a visitor fills out a form on Site A with their name and email, Site B knows their name and email too as soon as they land on the site.

Nix became aware of this when the network, identified by others as LeadLander, emailed him to promote the service. Curious but skeptical, he signed up for a demo and installed the network’s JavaScript on his site for a brief period. “As promised, I began to see personally identifying information about our anonymous visitors,” Nix wrote.

Wrong, but real

The posts by Suman and Nix have received a good amount of attention this week. And for good reason: what appears to have taken place has revealed a privacy can of worms many are learning about for the first time and has highlighted activity that may even be illegal.

Privacy cans of worms like this are bad news for the advertising industry, which is battling the notion that it simply can’t police itself and needs to be more tightly regulated. Regulated by bureaucrats whose medicines are often worse than the illnesses.

Email addresses are not created equal

Unfortunately, networks like LeadLander exist for a simple reason: many companies overestimate the value of an email address.

Savvy, experienced email marketers understand that the value of an email address is highly variable. For obvious reasons, the email address of a loyal customer who has opted in to a list is, for instance, likely to be much higher than the email address of a prospective customer obtained through a list broker, even if the list broker is selling an opt-in list.

So what’s the value of an email address of an individual who visited your website but didn’t provide you with her email address? In reality, it’s probably not all that high, but for companies like uberVU, it’s perceived to be high enough to warrant the use of a questionable service to obtain.

It’s the ‘how’ and ‘why’, not the ‘what’

The bad news for uberVU, of course, was that acquiring Sumit Suman’s email address did not prove fruitful because Suman was obviously not interested in uberVU’s services, at least at the time he decided to leave uberVU’s website. Reaching out to Suman via the questionably-acquired email address didn’t change that; instead, it led to a social media black eye for the social media marketing firm.

The reason: uberVU focused on the what — Suman’s email address — and not the how and why. How you acquire the email address of a customer or potential customer matters, as does the reason why the individual provided it.

Businesses that use email marketing successfully understand that a large portion of the value of their email addresses comes from the how and why and companies trying to bolster their email efforts should recognize that without a legitimate how and compelling why, the what isn’t all that valuable.