For instance, it uses U.S. Postal Service data to determine when someone has moved--a "trigger event" that may mean a consumer is in the market for certain types of items, such as kitchenware.

FORBES: Consumer Spy

On July 9, 2004, with the assistance of Mr. Veitch and professional movers, Ms. Ingle moved most of her furniture and personal effects remaining in the New York City apartment to the apartment in Johnson City, Tennessee, with some items, such as kitchenware, going into storage in Boston, Massachusetts, in anticipation of leasing an apartment there.

FORBES: Manhattan Spring Costs Internet Executive Quarter Million in State and City Tax