Customer Data Integration (CDI) is an essential part of a succssful CRM implementation.
Without it, it is impossible to establish a 'Single View of the Customer' and very difficult to obtain any useful metrics from your CRM System.
CDI is the first step in a Strategy for Customer Data Management.
This will typically start with CDI and then progress to Customer Demographics, Profiling, identification of Good and Bad Customers,
Propensity Analysis, Loyalty Retention and so on.