From the flash-from-the-past department (via PCWorld and SEW):
That banner ad you see today on a Yahoo Web page may have been triggered by a search you did on the company’s search engine two days ago.
That is because Yahoo tracks users’ queries on its search engine and, based on that information, tailors the graphical ads it beams at them later throughout its network of sites, a Yahoo official said Thursday.
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Yahoo Impulse tracks queries through users’ Yahoo cookies and serves up the subsequent graphical ads for 48 hours afterward, a company spokeswoman said. Yahoo Impulse has existed for about four years, but ads previously were triggered for only a 1-hour period after the user’s search session, she said.
This particular incarnation of Yahoo Impulse, with the much longer 48-hour ad tailoring period, was launched about three months ago, she said. Advertisers sign up for the program, but it’s not an opt-in program for users, she said.
This means that users aren’t asked for their permission to have ads tailored to them based on their search queries. However, the spokeswoman pointed out that this type of ad-customization activity is noted in Yahoo’s privacy policy.