OAuth addresses the following concerns:
To provide access to protected resources, users share their credentials in clear text with third-party applications. Potential security breaches can result from the ability of third-party applications to store a user's credentials for future use.
The inability of resource owners to restrict a client application's access to protected resources for a specified duration or to limit the client application's access to a subset of resources.
The inability of resource owners to revoke a client application's access to a specific client application.