his information, it can display ads based on what these habits suggest about her interests. For instance, advertisers might display ads about sporting events to people who visit sports-oriented sites. If a user fills out forms at any of the sites she visits while being tracked, the track- ing software has access to the information on the form. This allows advertisers to gather more detailed demographic information. Information gathered in this manner from sites such as social networks is a powerful way to attract advertisers. In turn, advertis- ing networks that place ads at many different sites are able to amass large databases demographic information about a user's browsing and purchasing habits. Mining this data and tailoring it for ad campaigns is referred to as behavioral advertising. Another way that marketers collect information about users is from online games on social networks such as Facebook. Every time a Facebook member downloads a game application, the game developer acquires information about the game player. Developers track the user's data, compile it into lists along with information about other users, and then sell the data to marketers. Marketing firms and manufacturers who purchase these databases use the infor- mation to show ads to people based on metrics such as age, gender, circle of friends, interests, and income. The software that tracks a user's browsing habits is becom- ing increasingly sophisticated and difficult to remove. A major problem with tracking software is that unlike older cookies, which only gathered information from a single location, tracking software follows users from site to site, monitoring their behavior while online. It is somewhat straightforward to delete cookies from browsers. This is not the case with tracking software. There are currently no menu commands in browser software to delete tracking files. Privacy versus the Bottom Line Large search, social networking, and e-commerce providers are under pressure from advertisers and investors to allow marketing firm