The hottest thing in direct marketing today is targeting individuals online vs. targeting via publishers or content. The idea that we can "know" a user and target them frees up the 90% of online inventory currently referred to as "remnant" space-- e.g. the space left over after GM, Microsoft and Coke buy the top page banners at Washington Post and NY Times. The remnant space can be just as valuable as the prime space if we only knew who the users were. A user interested in gourmet cooking is still a user interested in gourmet cooking when she leaves the NY Times food page and goes to her hotmail account or to her son's preschool website. Verticalizing the internet is a potential solution. Or rather, verticalizing internet users. The internet is already as verticalized as it's ever going to be. So how would one verticalize internet users? First of all, it's only going to happen on specific networks of sites.…