Enabling data sharing in your project using Google mobile developer services helps Google provide better services for you. This setting lets you securely share with Google the data that you collect using a Google mobile developer services data collection method (like the mobile SDKs). This setting only shares the data you collect using Google mobile developer services: it does not apply to data about your Google mobile developer services account or how your account is used, like the number of apps and which additional features are set up.
You can turn on this setting upon creating a project. This setting cannot currently be edited after initial creation of a project.