The Internet service provider, which provides broadband to around 2.8 million subscribers, previously said it would begin working with Redwood City, Calif.-based behavioral targeting company NebuAd on a trial basis by no later than June 15. But St. Louis-based Charter Communications, currently under pressure from privacy advocates as well as Congress, has not yet started the tests. The company has not yet set a new date by which it will begin the program.

A Charter spokesperson attributed the delay to technology issues. "It will happen when we're technologically ready," the spokesperson told Online Media Daily.

Two lawmakers, Reps. Edward Markey (D-Mass.) and Joe Barton (R-Texas), recently wrote to Charter CEO Neil Smith to ask that he delay moving forward with the pilot program until they could study the privacy implications of the arrangement. Charter met with the Congress members recently, but a spokesperson denied that the investigation was behind the delay.

Privacy advocates are worried about online ad targeting generally, but are especially concerned about the prospect of Internet service providers sharing data with ad companies. One of the main reasons is that Internet access companies have access to users' entire clickstream data--including every site visited and every search query entered. Older behavioral targeting companies only know when users visit a limited number of sites. Net neutrality organizations also have protested Charter's plans, arguing that Internet service providers should not examine users' Web activity.

A spokesman for NebuAd said CEO Bob Dykes was not available to comment about the delay. Dykes has previously said the system will respect users' privacy, and that all data collection will be anonymous. But privacy advocates contend that the platform will gather enough information about specific users that they can be identified even without their names or addresses.