I'm not sure how much this will be used, but TiVo has issued an upgrade that allows viewers to send personal information to advertisers. The Washington Post explains:

TiVo will now give advertisers direct access to viewers who are interested in their wares. The digital video recorder (DVR) maker said the upgrade lets some 1 million of its Series 2 stand-alone subscribers instantly respond to specially encoded advertising.

However, TiVo says the changes will not affect the way users normally view shows and skip ads, and will not force them to watch any ads they choose to ignore.

Under the new system, consumers can select an option to tell TiVo to release their contact information to an advertiser. For example, after watching an ad for an automobile or family vacation, users can use the remote control to request a brochure be sent to their home.

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