Somewhere inside your CRM is a customer who does not exist. They open emails at impossible hours. They redeem promotions with machine-like precision. They browse product pages across three devices in under five minutes. They convert, unsubscribe, re-engage and transact again. On paper, they look highly active. In reality, they may be a composite of behaviors stitched together from AI assistants, shared accounts, recycled addresses, autofill tools and automated workflows. This is the Data Doppelgänger Problem. And it is about to become one of the most expensive blind spots in modern marketing. For years, identity resolution was framed as a hygiene issue. Clean the data. Remove duplicates. Suppress invalid records. That work still matters. But the ground has shifted. Today, the bigger risk is not dirty data. It is convincing data that is wrong. AI agents are no longer theoretical. Consumers are using them to summarize emails, compare products, track prices, fill forms and in some cases complete purchases.…