Campaigns are far less effective at winning and retaining customers than they once were. To achieve sustainable competitive advantage, B2C marketers must deliver self-perpetuating cycles of real-time, two-way, insight-driven interactions with individual customers. Brands that seize this potential are assembling enterprise marketing technology ecosystems that Forrester calls contextual marketing engines to create highly engaging environments that drive business growth. This is an update of a previously published report; Forrester reviews and updates it periodically for continued relevance and accuracy; this version was revised with new data.