You may bring users to the trust network, providing them with unique value in helping them to better manage how they login to sites, apps and services in a more privacy preserving way. You will also get to consume user credentials that initiated from other sites, apps and services in the network when already credentialed users choose to engage and permission your service, streamlining user access.
The users you bring into the network will be permissioned for your service. If they choose to sign in to another service in the network, it does not change the relationship you have with your customer. In addition, the unique data sets necessary to deliver your services are assigned to your service and are not available to the network. Provisioning and accepting a privacy preserving consumer credential will yield greater trust and should help ease and enable adoption.