• by Wendy Davis , Staff Writer @wendyndavis, March 14, 2014

Last year, around 3.9 million Web users visited the Network Advertising Initiative's opt-out site, where they can opt out of receiving  “interest-based” ads, according to the group's annual compliance report.

Of those people, more than 600,000 opted out, says Marc Groman, executive director of the group. The NAI also reported that, for the most part, its members opt-outs worked as intended. While the group's automated crawler found some glitches, they were resolved within 24 hours.

Nonetheless, some consumers who attempted to opt out nonetheless reported trouble doing so -- often because the opt-outs are cookie-based, and cookies can be problematic. Among other issues, consumers often delete third-party cookies -- including the cookies that tell ad networks users have opted out of receiving targeted ads.

The group says in its report that around 8,000 consumers contacted it by email or via a link on the group's site; around 70% of them wanted to report a problem with an opt-out link. The NAI says that most of the questions came from “browsers or anti-virus software that blocked third-party cookies.” Any mechanism that blocks third-party cookies also prevents opt-out cookies from being set -- though those mechanisms often also would prevent behavioral targeting.

The organization says that other problems with the opt outs were due to factors beyond its members' control -- including “the consumer’s corporate network security, telecommunications breakdowns, and ISP or infrastructure anomalies.”

Currently, more than 90 ad networks (and other ad tech companies that collect data or serve ads) belong to the NAI. Last year, the organization reviewed 88 members to determine whether they complied with the group's privacy code. None of those members ere found to be “materially” out of compliance with its privacy code. The group's code requires ad networks to notify people about behavioral targeting -- loosely defined as ads that are served because people have visited particular sites in the past -- and allow them to opt out of receiving those ads. (The code also requires that companies obtain users' opt-in consent using certain types of information, like social security numbers; all of the members reviewed last year said they didn't draw on that type of data.)

But even though the NAI didn't find any major problems, it asked a few companies to tweak their Web sites, such as by making certain privacy-related links more prominent, according to Groman.

Last year, the NAI also adopted a mobile code, which sets out rules for serving ads based on data collected across more than one app. Those rules require companies to let people opt out of receiving behaviorally targeted ads on mobile devices. The report issued this week didn't address whether companies are complying with the new mobile code.