A lot of ink has been spilled over the ascendance of media walled gardens in 2015. Their proposition is compelling: using deterministic customer identifications, companies like Google and Facebook provide marketers with the strongest cross-device targeting and measurement for advertising. But access to the walled gardens' audiences comes with certain conditions attached — one of which is the lack of visibility on event- or user-level data. This report evaluates the short- and long-term implications of consolidating spend with walled gardens in terms of not just media buying but also strategic customer intelligence.