One such network, Ringleader Digital, has unveiled its new "media stamp" -- a cookie-like item that creates and stores profiles about cell users based on the mobile sites they visit. Unlike online advertising cookies, however, the media stamps are stored on Ringleader Digital's servers and not browsers, which means users can't delete them.
Ringleader Digital collects information based on characteristics of the device, but says it can gather enough data this way to create unique, "anonymous" stamps for every mobile phone user.
"We track devices, not individuals," the company said in a privacy statement issued today. Ringleader Digital adds that it doesn't collect mobile phone number, names, addresses or other so-called "personally identifiable information."
But the notion that anything other than name, address or phone number is "anonymous" has been discredited for a long time now. Consider, nearly every privacy organization, not to mention U.S. courts and lawmakers, hold that people have a privacy interest in their IP addresses -- even though they weren't traditionally considered personally identifiable. One reason is because examining enough activity associated with the same IP address can reveal that user's identity -- as famously happened when AOL released search histories for 650,000 "anonymized" IP addresses. Thelma Arnold, formerly known as AOL User 4417749, was identified by The New York Times within days of the breach.
Cell phones are even more likely to be tied to a specific individual than an IP address. After all, one person sometimes connects to the Web from different IP addresses (at home and at work, for instance), just as family members might share the same IP address. But many users just have one cell phone, and they keep it with them all the time.
Unlike the doomed ISP-based behavioral targeting company NebuAd, the media stamp only collects information about users when they visit sites of participating publishers. That makes the company seem more similar to a Web-based behavioral targeting company like Tacoda or Revenue Science, and possibly more palatable to privacy advocates.
But, unlike the case with Tacoda, Revenue Science or other behavioral targeting companies, there is no way for consumers to avoid being tracked by Ringleader Digital. The company says people will be able to opt out of receiving targeted ads, but not out of the profile creation and storage. There's little chance that this kind of opt-out will satisfy privacy advocates.
For now, Ringleader Digital has signed up four publishers, including local search company go2 Media and mobile entertainment company Thumbplay. The mobile ad network plans to test the platform early next year.