• by Wendy Davis , Staff Writer @wendyndavis, April 14, 2011

Apple is preparing to join Mozilla and Microsoft in offering a do-not track tool for its browser that, when activated, will communicate to ad networks that users don't wish to be tracked.

The new feature will be available this summer, according to The Wall Street Journal. The move leaves Google's Chrome, which accounts for around 11% of the market, as the only browser without a do-not-track tool on the horizon.

But even as browser developers roll out tools to help users express their privacy preferences, significant questions remain about whether ad networks intend to honor do-not-track requests that come from browsers.

Currently, no specific law or self-regulatory principle makes reference to a browser-based do-not-track tool. But the self-regulatory principles make clear that ad networks should let users eschew behavioral targeting. It seems absurd for ad networks to take the position that they need only honor consumers' choices if they communicate their preferences by clicking on an opt-out link.

What's more, behavioral targeting companies that promise users they can opt out of online tracking and then don't honor browser-based opt-outs might be engaging in deceptive practices. That's a question of interpretation, but an aggressive Federal Trade Commission could take that position.

The reality is, a browser-based system is far simpler for users than either opting out site-by-site or through a self-regulatory page like AboutAd.info or the Network Advertising Initiative. Those groups provide for a single-click opt-out of around 60 ad networks, but a browser-based header informs every ad network -- and there are thought to be hundreds -- of users' preferences.

Additionally, the self-regulatory groups are still adding members, meaning that users who want to avoid all behavioral targeting must continually revisit the NAI or AboutAds sites to update their preferences. In other words, as a recent Carnegie Mellon study pointed out, the industry-run opt-out pages "do not adapt to changing membership."