• by Wendy Davis , Staff Writer @wendyndavis, December 13, 2012

An employee of commercial real estate firm 42floors has publicly called out an analytics company for engaging in some highly questionable privacy practices.

In a blog post this week, 42floors.com's Darren Nix outlines how a Web company approached him and offered to provide him with email addresses of visitors to the site -- visitors who were under the mistaken impression that they were browsing anonymously. Nix didn't name the company in the original post because he didn't want to give it any advertising, but the Twitterverse quickly identified it as LeadLander; Nix confirmed to MediaPost today that the company was LeadLander.

Nix was curious how LeadLander accomplished this, so he requested more information. LeadLander's response, which Nix posted, indicates that it collects email addresses from sites that ask for users to submit such data. Next, LeadLander appends those addresses to users' "anonymous" cookies. That way, when they browse the Web, any publisher that installs LeadLander's technology can learn those users' email addresses.

Nix, a coder who currently is responsible for drawing new users to 42floors.com, was appalled by the prospect of discovering people's email addresses this way. But he was also skeptical about whether LeadLander could really deliver on its promise. So he decided to test the technology for himself. "I signed up for a demo account and installed (and hastily removed) the tracker," he says. "As promised, I began to see personally identifying information about our anonymous visitors."

LeadLander boasts on its site that it provides analytics for more than 4,000 companies, including some major brands. At this point, it isn't known how many of its clients are using an email appending service, as opposed to more traditional analytics.

In any event, 42floors.com isn't among them. "It's not a gray line," Nix says. "It's so blatantly wrong."

LeadLander hasn't responded to requests for comment, so it's not clear how long LeadLander might have used this technology. But Nix says he investigated after receiving LeadLander's pitch and that the particular tracker apparently used to glean email addresses first surfaced in 2011.

At one time there was widespread agreement that online ad companies wouldn't link email addresses and other so-called personally identifiable information to non-personally identifiable information, like cookies. But given the recent growth in data-driven marketing, companies like LeadLander apparently feel free to disregard that long-established norm.