• by Wendy Davis , Staff Writer @wendyndavis, February 18, 2011

The self-regulatory group Network Advertising Initiative proposed on Friday that behavioral advertisers who target Web users based on health-related data should disclose more information about the types of ads they serve.

Specifically, the NAI says that ad networks involved in tracking people in order to display health-related ads should also publicly state which health categories they serve targeted ads for. These categories potentially could include general health-related matters like "wellness," or more specific ones like "arthritis" or "hypertension."

The proposal, issued in the NAI's 2010 compliance report, came about in response to the NAI's troubling discovery last year that one of its member companies was violating its policy by targeting Web users based on health-related data without first obtaining their explicit consent. The NAI requires ad networks collecting sensitive data -- including medical and other health-related information -- to obtain users' opt-in consent even when the ad networks aren't also collecting users' names.

That wasn't the only questionable activity noted by NAI. The organization also reported that even though all of the members theoretically allowed users to opt out of online tracking, the opt-outs didn't always work.

"NAI staff believes that these issues were partly attributable to the member companies involved not having fully anticipated potential risks to opt out cookie mechanisms during systems migrations, and insufficient testing of opt out functionality following those changes," the report states. The group recommended that all members adopt practices aimed at making sure that systems changes don't knock out users' opt-out cookies.

The NAI also reported that around 2.3 million Web users visited its opt-out page last year, marking a 127% increase from 2009. Nearly half a million of them (472,000) opted out of online tracking, marking a 58% increase from the prior year.