She probably only left her address and phone number at a few websites and applied for some savings cards. The people calling don't really care that I'm not Rachel, they are just looking for someone that fits her profile. But this could change in the future. Companies that use data mining are currently most interested in who buys their products in the sense that they want to know where these consumers live, what their income is and how old they are. Not the actual consumer matters but her demographics.
Data miners sell the data they gathered accordingly.
They tell the new Circuit City that the neighborhood they are in has a high percentage of teenagers from wealthy families. As a result, Circuit City stocks up on Playstation 2's and the latest sensation in teen bands. Data miners have been digging a little deeper though and Circuit City now also knows the approximate number of families that own dvd-players and quite possibly also their addresses. If it wanted to it could approach this group directly with offers tailored to fit their appliances. Companies also mine data themselves through savings cards or membership programs.