"Facebook offers marketers the option to target ads according to data compiled by firms like Experian, Acxiom and Epsilon, which have historically fueled mailin

"Facebook offers marketers the option to target ads according to data compiled by firms like Experian, Acxiom and Epsilon, which have historically fueled mailing lists and other sorts of offline efforts. These firms build their profiles over a period of years, gathering data from government and public records, consumer contests, warranties and surveys, and private commercial sources — like loyalty card purchase histories or magazine subscription lists."