Salesforce exposes information relating to the use of your package components in subscriber orgs. This enables you to report what Custom Objects and Visualforce pages your customers are using and, more importantly, those they are not. This information is provided by Salesforce and cannot be opted out of by the customer.

This facility needs to be enabled by Salesforce Support. Once enabled, the MetricsDataFile object is available in your production org and will receive a data file periodically that contains the metric's records. The Usage Metrics Visualization application can be found by searching on AppExchange, and can help with visualizing this information.